Preventing Residential Growth From Causing School Overcrowding & Excessive Class Size

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Excessive residential development is not the only reason for school overcrowding, but it is the most preventable. By development we mean proposals to build new shopping centers, housing projects, highways, and so forth. But when it comes to school impacts we’re mostly talking about residential development. After all, it is only new homes, townhouses, apartments and other residential growth which adds students to schools.

If you’re concerned about how growth may affect schools anywhere in the USA then contact CEDS at 410-654-3021 (call-text) or for an initial no-cost discussion of strategy options.  

States With The Least School Overcrowding & Best Pupil:Teacher Ratios

Increasing class size and overcrowded schools are the greatest impact of poorly managed growth. If school expansion and construction of new schools does not keep pace with increasing student enrollment then student performance may decline along with the quality of the school experience for students, their families and teachers.

The chart above shows the average ratio of pupils to teachers in the 50 states for the 2013-2014 school year. A ratio of more than 20 students per teacher is generally considered undesirable. In fact, 12 states have adopted laws requiring a ratio of 20 students or less per teacher.

Note that the pupil:teacher ratio is NOT the same as average class size. For example, to get average class size for grades K-3, one must add 9 or 10 students to the pupil:teacher ratio.

The darkest blue states above generally have the most severe overcrowding problems. But overcrowded school districts can be found within many of the other districts. By the 2024-2025 school year, the number of students attending public schools will increase by 6%. This trend is not uniform. Nevada will experience a 26% increase in enrollment by 2024 while that of West Virginia will decline by 11%.

Preventing School Overcrowding Is Easy

We assume you’re visiting this webpage because you’re concerned about how a proposed development project may impact local schools. If you are like most folks new to this form of advocacy you probably think its both difficult and expensive to prevent the impact. The good news is that its actually quite easy. And you probably don’t need a lawyer or any other professionals.

The reason is that its easy is because few issues generate as much public ire as the prospect of development causing school overcrowding. By turning public ire into political momentum you can get reforms enacted which allow your locality to continue reaping the benefits of growth without having a negative impact to schools. In fact, done right, the reforms should improve the quality of education.

We call this approach Equitable Solutions. We have a webpage devoted to the approach where you’ll find detailed advice on how to make it work for you: Equitable Solutions webpage. And when political action alone doesn’t carry the day, the CEDS Smart Legal Strategies approach usually allows our clients to prevail.

Why School Overcrowding Is A Problem

The research summarized below indicates that when enrollment greatly exceeds the design capacity of a school that student academic performance declines along with the “enjoyability” of school for students, faculty and parents. Here are some of the impacts not cited in the research:

  • A portion of the students may be forced to eat lunch early or late in the day.
  • Traffic congestion and pedestrian safety becomes more of a problem at pick-up and drop-off times.
  • Only a portion of parents can fit into the cafeteria or auditorium to see their child perform.
  • Parents of high school seniors may be forced to watch their kid graduate on closed-circuit TV.

an effective learning environment?Clicking on the green text below will take you to the scientific study quoted. One of the things which may strike you is the frequent expressions of uncertainty with regard to findings.

California schools have long been among the most crowded in the nation. A 2007 report characterized the impact as:

“Overcrowding creates unsafe environments and makes teaching and learning more difficult. Schools may need to teach students in auditoriums, gymnasiums, storage rooms, and other areas never intended to be used for instructional purposes. Schools with too little space may not be able to maintain specially equipped rooms such as science labs or libraries because these spaces need to be “flexible” for teaching multiple subjects.”

A study of factors affecting the number of high school students going on to college noted:

“Overcrowding reduces students’ ability to pay attention and increases school violence. In such schools, students achieve less; rates of teacher and student absenteeism are higher than at schools that do not have these problems. Sometimes overcrowding is addressed by putting students on year-round, multi-track schedules with fewer days of school. These students suffer interrupted and lost instructional time; limited access to advanced courses and specialized programs; ill timed breaks and correspondingly limited access to extracurricular activities and enrichment programs; and poorer academic performance.”

Research shows that school overcrowding has varying effects on student achievement. A North Carolina study noted that:

“Severely crowded schools [>130% of capacity] have a negative impact on reading achievement, but no discernible impact on math achievement.”

Research has also linked overcrowded schools to increased bullying.

Of course, overcrowding has an impact on teacher effectiveness and job satisfaction. A 2012 study of the relationship between school variables and teacher satisfaction, contained the following conclusion:

“As school budgets decrease and the numbers of students increase, it is critical that school districts continue to invest in efforts that will keep class sizes from becoming too large. Perhaps smaller class sizes allow teachers to work with students who show problematic behaviors or students with community challenges such as poverty and under preparedness more effectively; this idea will need to be explored through further study. Nevertheless, smaller class sizes help teachers to be more satisfied with their jobs and smaller class sizes have also been shown to positively affect student achievement.”

The U.S. Department of Education notes that overcrowding increases wear and tear on a school.

Why Overcrowded Classrooms Are A Problem

As of the year 2016, USA class size averaged 15 students in public schools and 12.2 students for private schools. As stated above, this ratio is NOT the same as average class size. For example, to get average class size for grades K-3, one must add 9 or 10 students to the pupil:teacher ratio.

According to a 2011 Brookings Institution report, 24 states require or actively promote a reduction in class size. However, changing the national class size average by just one student costs $12 billion per year in just teacher salaries.

Most discussions of the effect of class size on student performance begin with Project STAR (Student-Teacher Achievement Ratio) conducted in Tennessee beginning in 1985. Two Kindergarten to 3rd grade class sizes were compared over a four-year period: 13 – 17 students per classroom and 22 – 25 students. The principal finding was that the smaller class size:

“produce substantial improvement in early learning and cognitive studies and that the effect of small class size on the achievement of minority children was initially about double that observed for majority children, but in later years, it was about the same.”

While the difference in performance of minority and majority students disappeared in subsequent years, the students who benefited from the smaller K-3 class size continued to outperform students who were in the larger class sizes. A 2010 follow-up study showed that the benefits of smaller K-3 class size and above-average teachers extended into adult life!

Subsequent studies have followed the students into adulthood and documented the following benefits:

  • 72% of STAR students graduated on time vs. 65% of other students;
  • STAR students completed more advanced math and English courses in high school;
  • Drop-out rates among STAR students was 19% vs. 23% for others;
  • More STAR students graduated with honors, and
  • As noted above, a 2010 follow-up study showed that the benefits of smaller K-3 class size and above-average teachers extended into adult life!

The authors of the Brookings report cited earlier noted that while the most credible studies of class size and student performance do show an improvement with fewer students per teacher, the benefit is not uniform and, overall, it may be relatively small. The problem is that there are simply too few high quality studies to draw any firm conclusions about the benefits of class-size reduction. The research indicates students in the smaller classes performed at the same level as students with three more months of school.

Class-size reduction has the greatest benefit for Kindergarten to Third Grade students from disadvantaged backgrounds. Other actions that result in expanding the number of highly effective teachers may be more beneficial. But there is some evidence indicating that a smaller class-size can contribute to better student performance when the teacher is less well prepared and effective.

One study cited in the Brookings report noted that the following actions were more beneficial than class size reduction: computer-aided instruction, cross-age tutoring, early childhood programs, and increases in per student instructional time.

However, given the tremendous investment in class-size reduction it would be unthinkable to abandon this effort and return to larger classes before the benefits have been thoroughly examined. In the meantime, parents should aggressively oppose any action – or inaction – that allows schools and classrooms to become more crowded.

Will A Development Proposal Cause School Overcrowding

How do you determine if a proposed development project will cause school overcrowding? Well, if a school has portable classrooms that are currently in use or average class size is in excess of 30 students, then you can probably assume it is overcapacity. Otherwise, you’ll need to know:

  • current and projected school capacity;
  • current and projected enrollment;
  • the number of students added by the project; and
  • how many students will come from other development proposals not yet built.

If your locality has concurrency or Adequate Public Facility requirements then this data should be readily available.

Try doing an internet search on the keywords “school” + “concurrency” + “adequate public facilities” + “name of your town, city or county”. If this yields nothing then search for the master plan for your town, city or county and for the school system. If recent, either plan may contain the data you need. Otherwise, try the following steps.

School Capacity & Enrollment

Try an internet search using the keywords “capacity” + “the school name”. If this yields nothing then contact the officials who oversee the school system (Board of Education, School Board, etc.). Ask if they have data on the capacity and enrollment of the three schools potentially affected by the project (elementary, middle and high school). Of course they should have this data and it should be freely provided. You could also try staff at each school, PTA officers or the school faculty. Another option would be the education department for your state.

Project Impact

To estimate the impact of a project proposal on student enrollment you need to know the effect of similar housing in your area. If you’re lucky the local or State education department has this data in the form of pupil yield tables. If not, then you may need to do some calculations.

On average, each U.S. household contributes 0.43 students to public schools. About 70% of these students are in Pre-K to 8th grade, the rest are in 9th to 12th grade. Of course pupil generation rates vary considerably across the country and even within school districts. They also vary by housing type.

In my locality (Baltimore County, MD) a rental apartment may generate 0.0173 elementary (K-5) students per year while a single-family detached homes yields 0.179. Depending upon where the single-family detached home is located, the yield may range from 0.088 to 0.298 elementary students per year. Variables accounting for this range include house size, income level, age, and other factors.
Student yields also vary with age of housing.

According to the 2015 American Housing Survey, homes built between 2010 and 2015 had 26% more occupants under the age of 18 when compared with all homes. This indicates that the number of students coming from newer homes could be as much as 26% higher than the average.

To get a rough estimate of impact divide the number of elementary, middle and high-school students attending public schools in your locality by the number of housing units. Next, find out how many housing units are proposed with regard to the project of concern to you. You can then multiply the number of units by the ratios for elementary, middle and high school. Add these values to current enrollment for each of the three schools impacted by the project to see if this causes enrollment to exceed school capacity. To see an example of this analysis go to page 9 in our Ann Arbor report.

Other Projects

If the preceding analysis did not show that school capacity would be exceeded, then you may wish to take into account other project proposals that are moving through the review pipeline. Development tends to cluster in space and time which may mean that other projects have been proposed for the same general area. Your local planning and zoning staff can tell you of any other projects. If staff are not helpful then look at past planning commission minutes for other projects in your area. Consult maps prepared by the local school board of the service area of each school to see if a project is within the boundaries.

Preventing School Overcrowding

The U.S. Department of Education defines an overcrowded school as one where enrollment is 5% above the design capacity. As of the year 2000, 22% of U.S. schools were overcrowded. For example, Maryland assumes a design capacity of 23 students per Grade 1 – 5 classroom. A school with 20 Grade 1 – 5 classrooms could accommodate 460 students plus Pre-K and K.

To prevent overcrowding, school expansion and new school construction must keep pace with increases in student enrollment. While mechanisms are available for limiting increases in student enrollment, these can only be used as short term solutions.

A number of states have adopted class size limits. Education Week produced a map showing the limits adopted by each state. However, the adoption of a limit does not necessarily allow local government to say no to development proposals that could cause individual schools or a school district to become overcrowded. For this you need something like an Adequate Public Facilities Ordinance.

Adequate Public Facility Ordinance

Arizona, California, Florida, Maryland, Montana, North Carolina, Washington and Wisconsin are among the states where local governments utilize an Adequate Public Facilities Ordinance (APFO). With regard to schools, the APFO will prohibit the issuance of a building permit if the construction of the home authorized by the permit would cause a school to exceed a capacity threshold. Some localities allow developers to pay for the cost to expand schools and thereby proceed with development as the added capacity becomes available. In addition to schools, an APFO may also apply to traffic congestion, water and sewer capacity, or emergency services.

Depending upon how the APFO is written, the permit issuance may be withheld for a year or two and even longer, but not indefinitely. However, one State Supreme Court did uphold an 18-year postponement and the U.S. Supreme Court upheld a 32-month postponement.

To see an example of how APFO school overcrowding protection can vary in effectiveness within a state, see the CEDS report How Successful Are Maryland Counties In Preventing School Overcrowding.  And for an example of the effect of zoning changes on school overcrowding see Assessing School, Traffic & Environmental Effects of Rezoning Requests.

APFOs may also be known as concurrency criterion. In this context, concurrency means that it must be demonstrated that infrastructure (schools, roads, etc.) have the capacity to accommodate a development project without undue impact.

There is a legal theory that State legislative authorization may not be needed to adopt APFO-like restrictions. The theory is that the power to restrict growth which would cause excessive impact may be inherent in zoning and other growth management powers already granted to local government by the State legislature.

For further information on Adequate Public Facility laws see:

Master Plan

The prevention of overcrowding begins with a comprehensive, long range master planning process. To see an example of the type of school capacity-projected enrollment data all master plans should include, visit the CEDS Growth Plans webpage. 

The organization in charge of schools (Board of Education, School Board, etc.) develops a plan showing anticipated changes in student enrollment and school capacity. The local legislative body (county-city council, board of supervisors-alderman, etc.) adopts a master plan for how future growth will be managed. Policies are adopted with regard to classroom size and what degree of school overcrowded will be permitted, which should be none. The two plans are adjusted to minimize the probability that class size will be exceeded due to school overcrowding.

This planning process usually works fine as long as growth and other factors proceed as anticipated. Many localities update their plans every five or six years to respond to changes. Others adopt local or sector plans to account for the unique characteristics of specific areas within a town, city or county.

A major unanticipated event was the 2008 recession. Since the start of the recession in 2008, state funding for schools has declined. In fact, 35 states now spend less on school infrastructure when compared to pre-2008 figures. The recession caused a slow-down in the new residential development which adds students as well as school expansion or new school construction. While you would think the two would balance out, many localities are adding portable classrooms while adjacent jurisdictions are closing recently completed new schools.

In some states a local government can deny approval for a proposed development project which conflicts with a master plan element such as one prohibiting school overcrowding. But in many states the prohibition must also appear in the zoning ordinance or other regulations. And in some the State legislature must first adopt enabling legislation allowing local governments to restrict growth causing overcrowding. An example is an Adequate Public Facility Ordinance.


A local government can expand the area it regulates through a process known as annexation. Usually an area adjoining a town or city is annexed into the municipal boundary. In most cases the majority of property owners within the proposed annexation area must agree. However, the process is usually initiated by a development company seeking access to water and sewer services which then allow a property to be development far more intensely when compared to that possible with well and septic. Frequently there must be a finding that the annexation is consistent will the master plan. In fact, responsible growth management dictates that an annexation should not be considered unless it was studied during the last master plan update and found to have a positive effect on the quality of life of all residents. A key finding should have been that the annexation will not result in school overcrowding.  For further detail visit the CEDS Annexation webpage.


Through zoning a local government determines what uses may be made of a portion or every parcel of land within its boundaries. The Zoning Ordinance will also set forth limits such as number of housing units per acre, height limits, setbacks from property lines, etc. In many localities the range in housing units allowed per acre ranges from 0.10 to 16 or more. So a ten acre project might be developed as just one home or more than 160 apartments. The number of students added to local schools could vary accordingly.

For an example of the effect of zoning changes on school overcrowding see Assessing School, Traffic & Environmental Effects of Rezoning Requests.

In most localities, the final decision-maker on rezoning requests is the legislative body. If your locality has a mayor or county executive and a city-county council, then it is the council which makes the decision on rezoning petitions. Master plan conformance will be one of the primary decision-making criteria with regard to a rezoning. If your master plan sets the goal of preventing school overcrowding and you present data showing overcrowding will occur then you may win provided you pursue the general advice provided on our Equitable Solutions and Smart Legal Strategies webpages. Rezoning decisions tend to be driven as much by politics as fact and law. If the master plan is silent on school impacts you may still convince the decision-making body to say no by mobilizing the support of parents of the students attending the impacted schools. For further detail on this strategy option see Chapters 36 and 39 in the free CEDS book How To Win Land Development Issues.

Conditional Uses & Special Exceptions

Most zoning ordinances will list uses allowed “By-Right” and those requiring a Conditional Use or Special Exception Permit. The uses allowed with the Permit are generally compatible with others allowed within a given zoning district, but occasionally may cause undue impacts. It is for this reason that an applicant seeking approval for the Condition Use-Special Exception Permit is usually required to go through a hearing process.

The purpose of the hearing is to determine if any undue impacts may occur. If impacts are found to be likely then conditions may be imposed that will resolve the impact. If impacts will be excessive then the Permit may be denied. Some of many possible conditions which may resolve excessive school impacts are:

  • postponing the project until school capacity is increased;
  • providing a new school site;
  • paying for a portion of the cost of increasing school capacity; or
  • improving the safety of students walking to school by putting in sidewalks, trails or bike lanes.

For further detail visit the CEDS Conditional Use & Special Exception webpage.

School Overcrowding Solutions

One of the more extensive reviews of relevant literature led three researchers to conclude that the best solution to school overcrowding was to build more schools; not to add portable classrooms or to initiate year-round schooling.

Impact Fees

Increasingly people resist paying the additional taxes needed to cover the cost of providing new roads, water and sewer services and schools required for new development. One option to generate additional funds for these and other infrastructure needs is to charge development companies an impact fee to cover the cost of school expansions or new school construction. Impact fees are also assessed to cover the costs of building new roads, extending water-sewer lines and for other infrastructure needs.

As of 2015, 29 states had passed legislation allowing local governments to charge impact fees. In 1987, Texas became the first to adopt this legislation.

School impact fees are only required for residential development. The fees vary by housing type based on pupil generation – the more students coming from a housing type, the higher the fee. Impact fees are based on the per student cost to construct school buildings and other infrastructure. Ongoing expenses like teacher salaries are not factored into the fee. Following is a sampling of school impacts fees.

Jurisdiction Impact Fee Per Single-Family Detached House

School Boundary Adjustment

If you have three elementary schools with abutting service areas and one is overcapacity while the other two have excess space, it makes sense to adjust the boundaries to resolve the issue. If such adjustments are rare then the overall impact is likely beneficial. However, some schools districts have gone from rare to frequent boundary adjustments.

Studies of students subject to frequent school changes show reduced performance. The U.S. General Accounting Office found that students who attend three or more schools by the 8th grade are at least four times more likely to drop out of school. A Texas study noted that 41% of highly-mobile students are low-achievers compared to 26% non-mobile students. These findings indicate that school boundary adjustments should remain rare.

Mobile Classrooms

Also known as portables or trailers, 31% of all U.S. schools had portable buildings as of the 2012-13 school year.

A 2004 study of California portable classrooms noted that many had significant cooling and ventilation problems. A similar study of Idaho and Washington state portable classrooms found that elevated carbon dioxide concentrations correlated with a 10% to 20% increase in student absence. A 2009 paper reported that:

“No significant impact of portable classrooms on teacher perception, teacher morale, teacher job satisfaction, student achievement, and behavior is detected. Negative student attitude is found in one of the studies reviewed. Technical testing shows negative relationships between portable classrooms and health and safety conditions, but the permanent structures are sometimes worse.”

Year-Round Calendar

Traditionally, students attend school for nine months (180 days) with summers off. This agrarian calendar is a remnant of the days when students were needed for summer farm work. A number of school districts have experimented with year-round schools as a solution to overcrowding. Also, the school day is extended with some students beginning early and others later in the day.

The pie-chart below illustrates a typical year-round calendar. The approach certainly makes more efficient use of available classroom space and should achieve a class-size reduction. Educators have long noted that over a long summer vacation students lose a portion of what they learned during the previous school year. So, in theory, a shorter summer gap should improve academic performance. But available research indicates student performance may decline.

In California researchers found that:

“Being on a multitrack year-round calendar results in a drop of 1–2 percentile points relative to a traditional calendar in national rank on reading, math and language scores.”

However, an exhaustive study of year-round schools in North Carolina found no significant difference in student performance.

A review of studies of extended school day and year programs from 1985 to 2009 revealed that definitive conclusions could not be drawn about the effects due to poor study design or flawed assessment methods.