Longitudinal Analysis of the Effectiveness of DCPS Teachers

Publisher: Washington, DC: Mathematica Policy Research
Jul 08, 2014
Authors
Elias Walsh and Dallas Dotter

This report addresses the following research questions to help education policymakers and practitioners understand how teacher retention and teacher effectiveness have changed over time in DCPS: 

1. Have retention rates of effective teachers changed since the first year of IMPACT? Because teachers who earn an ineffective rating in one year or a minimally effective rating for two consecutive years are dismissed under IMPACT, overall retention rates may fall even as effective teachers are retained at higher rates. We first examine how many teachers met IMPACT criteria for dismissal and were dismissed. We then compare the overall retention rate for teachers in the 2008–2009 school year, before IMPACT scores were calculated, to the overall retention rates in each of the first three years of IMPACT (the 2009–2010 to 2011–2012 school years). We also compare the rate at which DCPS retained its most effective teachers (measured by IMPACT) in the first year of IMPACT in 2009–2010 to the same rates in 2010–2011 and 2011–2012. Finally, we examine whether the rate at which individual schools retained teachers changed over time.

2. How effective are teachers who leave DCPS and teachers who are hired to replace them? Whether the average DCPS teacher was more effective four years after IMPACT began depends in part on whether DCPS retained its most effective teachers and hired new effective teachers to replace its least effective teachers. We examine the effectiveness of teachers who entered and exited DCPS since IMPACT was initiated compared to those “core teachers” who remained in DCPS from the 2008–2009 through the 2012–2013 school years. We calculate the gap between the average IMPACT scores of teachers who left DCPS in a given year and the core teachers in each year. We also calculate the gaps between the average IMPACT scores of teachers who were new to DCPS each year and the average IMPACT scores of core teachers.

3. How does the effectiveness of novice teachers change with experience? We measure changes in effectiveness for novice teachers as they become more experienced relative to the change in effectiveness for veteran teachers. Teachers typically become more effective as they gain experience, which is why novice teachers are usually less effective than veteran teachers. The success of IMPACT in improving teacher effectiveness may depend in part on whether and how much novice teachers improve over time compared to veteran teachers.