The Relationship Between Smaller Class Sizes and Better Student Outcomes

In recent articles, we have pointed out that Washington state is 46th in the nation in school funding as a percent of income. Washington state is also 46th in the nation in class sizes. It would take several billion dollars per year in additional funding to restore Washington state to the national average in school funding. One of the goals of restoring national average school funding is that it would allow us to hire tens of thousands of teachers needed to lower class sizes in Washington state down to the national average.

Sadly, there are many misleading claims made by those who oppose restoring school funding to the national average. For example, some claim that class sizes are not that high in Washington state. Others claim that reducing class sizes would not help improve student outcomes. In this article, we will clarify how to properly measure class size. We will then compare class sizes to other states and other nations. Finally, we will summarize the research on the significant long term benefits of lower class sizes.


Why Actual Class Sizes are Much Larger Than Student to Teacher Ratios
The most common mistake made when discussing class size is to confuse class sizes with Student to Teacher Ratios. The Student to Reacher Ratio is determined by dividing the total number of students in a school or a state by the total number of professional staff at the school or the state. For example, if you go to the Washington State OSPI website and click on Apportionment, then Publications, then Personnel Summary Reports, then select a year, then click on Table 46, you will get a report called “Ratio of Students to Classrooms.” This is actually the Student to Teacher Ratio. For the 2014 school year, this ratio was 18.2 students per teacher.

This type of statistic might mislead one into believing that the class sizes in Washington state are only 18 students – which would mean Washington state has the lowest class sizes in the nation and in the world. Yet if you walk into any real classroom at any real school in Washington state and count the actual students, you will see about 30 students in the real classroom. Many classrooms will have 35 to even 40 students! Why is there such a huge difference between the Student to Teacher ratio reported by OSPI and the number of students in real classrooms? The problem is that OSPI uses an extremely broad definition for classroom teacher. Many so-called classroom teachers are actually administrators and counselors. Using Student to Teacher ratios therefore misleads the public and even legislators into thinking that class sizes are not that bad when in fact class sizes in Washington state are among the highest in the nation.

A better estimate of classroom teachers comes from a national survey of classroom teachers in which teachers are asked how many students are in their average classroom. This survey indicates that for Grades 1 through 6, the national average class size is 21 students and the average class size in Washington state is 24 students. For Grades 7 through 12, the national average class size is 27 students and the average class size in Washington state is 30 students.