hers receive one of four ratings – highly effective, effective, minimally effective, or ineffective. Those rated ineffective (or minimally effective two years running) were dismissed. Total teacher turnover rates in the schools were higher (18% per year) than in similar non-participating schools (8-17%). Turnover rates among low-performing teachers (minimally effective or ineffective) were 46%, and for high-performing teachers (effective or highly effective) 13%.
The study found that there was a small increase in student achievement in mathematics (effect size of +0.079) that was statistically significant, and a smaller increase for reading (+0.046) which was not statistically significant. Turnover of high-performing teachers had a negative but not statistically significant effect on student achievement in mathematics (-0.055). Turnover of low-performing teachers improved student performance in mathematics (+0.21) and reading (+0.14).
The authors conclude that under a robust system of performance assessment, turnover of low-performing teachers can generate meaningful gains in student outcomes, particularly for the most disadvantaged students.
Source: Teacher Turnover, Teacher Quality, and Student Achievement in DCPS (2016), The National Bureau of Economic Research.