NCPA - National Center for Policy Analysis

Reducing Class Size Doesn't Improve Outcome

November 2, 1998

Among the touted benefits of the recently passed budget is increased federal aid to hire more teachers in order to reduce class size. Intuitively, it certainly seems true that a teacher with fewer students will be able to devote more time to each student, thus improving the quality of teaching. However, extensive research has failed to find any relationship between class size and educational outcomes, as measured by test scores. The fact is that pupil-teacher ratios have been falling for years as have test scores.

  • In the mid-1960s, the pupil-teacher ratio in public schools was 24.1 to 1 (see figure).
  • By the early 1990s, this ratio had fallen to just 17.3 to 1, a decline of 28 percent in class size.
  • Yet over this same period, average combined scholastic aptitude test (SAT) scores fell from 954 to 896, a decline of 58 points or 6 percent. (The SAT scale was rebased a few years ago, but these data are consistent over the period.)

University of Rochester economist Eric Hanushek found that in 277 statistical studies on class size and student achievement, only 15 percent showed a clear positive relationship. However, 13 percent actually showed a negative relationship, the rest having results that were not statistically significant.

Hanushek also points to the Tennessee experiment in the mid-1980s in which students were randomly assigned either to large or small classes. The results were statistically insignificant except for kindergartners, who showed significant improvement in smaller classes.

One reason why smaller classes have not aided student achievement is because large increases in hiring of teachers to reduce class size have forced schools to hire less qualified teachers.

 

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