The Effectiveness of Class Size Reduction

The Effectiveness of Class Size Reduction

The following post presents research or analyses from outside KASB and is presented for information purposes.  KASB neither endorses nor refutes the conclusions or recommendations contained herein.
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This month, the National Education Policy Center (NEPC) released a research review entitled “The Effectiveness of Class Size Reduction” The report gives a very good review of the research related to class size and student outcomes. You can read it here.

The report indicates that nationally teacher pay and benefits account for about 80% of the country’s school budgets. This is consistent with research KASB has done indicating that as of 2015, 77.8% of school expenditures went to salaries, benefits, and purchased (or contract) services. You can read KASB’s research here.

As early as 1979, there was research showing that once class size fell below 15 or so, “learning increased progressively as class size became smaller.” Further, the gains made by students in smaller classes lasted; as students in smaller classes early on were more likely to graduate, go to college, and get a college degree.

Critics including Eric Hanushek claim that class size is only relevant for certain groups of students, subjects, and teachers, that teacher quality is more important than class size, and that reducing student teacher ratios is very expensive and not demonstrably more effective than less expensive strategies.

Despite this criticism, based on the existing research as a whole, the author concludes that “the literature on class size reduction is clear and positive. The ‘overwhelming majority’ of peer-reviewed papers find it an effective strategy.” He goes on to present the following recommendations:
  • Class size is an important determinant of student outcomes, and one that can be directly determined by policy. All else being equal, lowering class sizes will improve student outcomes.
  • The payoff from class-size reduction is greater for low-income and minority children.  Conversely, increases in class size are likely to be especially harmful to these populations — who are already more likely to be subjected to large classes.
  • While lowering class size has a demonstrable cost, it may prove the more cost-effective policy overall particularly for disadvantaged students. Money saved today by increasing class sizes will likely result in additional substantial social and educational costs in the future.
  • Generally, class sizes of between 15 and 18 are recommended but variations are indicated. For example, band and physical education may require large classes while special education and some laboratory classes may require less. 

It is worth noting that KASB research has found that the average student-teacher ratio in Kansas, which is roughly analogous to class size, is approximately 18 students per regular teacher, and 9 students per direct educator. You can read more about Kansas student to staff ratios here.