The study looked at the effect of IMPACT, a performance assessment and incentive system introduced in schools in Washington, DC. IMPACT evaluates all teachers every year based on multiple measures of effectiveness (eg, clearly described standards, several teacher observations by different observers, and student outcomes). Teachers 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.