Class Size Reduction, Teacher Quality, and Academic Achievement in California Public Elementary Schools

In 1996, California passed a statewide class size reduction (CSR) law that aimed to reduce average class sizes in kindergarten through third grade by roughly one-third. Educators and policymakers expected CSR to lead to large gains in student achievement. However, increasing the state’s teaching workforce by thousands of new teachers had the potential to offset the direct benefits of smaller classes, particularly for schools in economically disadvantaged communities that already had staffing difficulties.,

In 1996, California passed a statewide class size reduction (CSR) law that aimed to reduce average class sizes by roughly one-third in kindergarten through third grade. Educators and policymakers expected CSR to lead to large gains in student achievement. However, increasing the state’s teaching workforce by thousands of new teachers had the potential to offset the direct benefits of smaller classes, particularly for schools in economically disadvantaged communities that already had staffing difficulties. This report addresses the following questions:

• What were the effects of CSR on overall teacher experience, certification, and education? Were some schools affected more than others?
• How did CSR affect student achievement? What were the benefits of smaller classes? What were the effects of new teachers?
• Are the benefits of smaller classes concentrated among a subset of students, or did all schools benefit equally from CSR?

The authors found that a ten-student reduction in class size raises the percentage of third-grade students who exceed national median test scores by roughly 4 percentage points in mathematics and 3 percentage points in reading. However, having a new teacher reduces the percentage of students who exceed national median test scores by roughly 3 percentage points in both mathematics and reading.

CSR led to a dramatic increase in the percentage of teachers who lacked full certification, who had no postgraduate education, and who were in their first or second year of teaching. These teachers were concentrated in schools with high percentages of nonwhite students enrolled in subsidized lunch programs.