A controversial teacher-evaluation system put in place by former District of Columbia Schools Chancellor Michelle Rhee has done what it was supposed to do, according to new findings: It makes low-performing teachers leave the school system and improves the skills of those who stick around.
The findings, out today from researchers at Stanford University and the University of Virginia, are unlikely to quell criticism of the so-called Impact system, which allows D.C. to fire teachers rated "ineffective" after just two years. High performers, meanwhile, qualify for an annual bonus of up to $25,000 or more for their entire careers.
The researchers found that Impact had an impact within two years: teachers with one "minimally effective" rating were much more likely than others to quit, but those who were rated "highly effective" stuck around and earned higher scores.
"Essentially what we found was they either left or got better," said Stanford's Thomas Dee, one of the researchers. "Those who remained performed substantially better, and did so over the multiple measures within Impact." Those include not just student test scores, but observations of their teaching, he said.