Tuesday, February 19, 2019

The relationship between school overcrowding and class size

In December, Class Size Matters released a report entitled The Impact of PreK on School Overcrowding: Lack of Planning, Lack of Space.  Our analysis showed that more than half of the 25,000 students who attended pre-K classes in DOE buildings in 2016-2017 were placed in 352 elementary schools that were over-utilized, meaning at 100 percent or above according to the DOE formula. leading to worse overcrowding for about 236,000 students.  In about one quarter of these schools, the expansion of pre-K actually forced the school to 100% or more.

A previous report we did on school overcrowding called Space Crunch goes into more detail on the impact of school overcrowding on the quality of education in NYC, everything from forcing kids to eat lunch as early as 10 AM, causing the loss of art and science rooms or libraries, and having fewer dedicated spaces for counseling and intervention, in many cases leading to special needs students receiving their services in hallways and closets.

Along with budget cuts, overcrowding has also contributed to larger class sizes in NYC schools, which have grown sharply since 2007, especially in the early grades K-3.  We had never precisely analyzed this relationship before, but decided to do so by looking at the average utilization rates in NYC elementary schools by district compared to their average class sizes in grades K-3.  The utilization rate is determined by a complex formula described in the Blue Book, the annual school enrollment, capacity and utilization volume that reports on how overcrowded a school is.

We found a very strong statistical relationship between the average utilization rate of each district's elementary schools and their average class sizes in grades K-3.   The correlation is 0.829, with a p value far below 0.001, which means it is highly significant.  


We also provide a chart below, showing which districts have higher and lower class sizes than their utilization rates might otherwise predict. 

That some districts fall above the line and others below is not surprising. The DOE utilization formula is far from perfect, and there are other issues that affect class size, including school budgets and school and district-specific priorities and policies.