Two years ago, we embarked on an ambitious effort to identify what works in fostering widespread teacher improvement. Our research spanned three large public school districts and one midsize charter school network. We surveyed more than 10,000 teachers and 500 school leaders and interviewed more than 100 staff members involved in teacher development.
Rather than test specific strategies to see if they produced results, we used multiple measures of performance to identify teachers who improved substantially, then looked for any experiences or attributes they had in common -- from the kind and amount of development activities in which they participated to the qualities of their schools and their mindset about growth -- that might distinguish them from teachers who did not improve. We used a broad definition of "professional development" to include efforts carried out by districts, schools and teachers themselves.
In the three districts we studied, which we believe are representative of large public school systems nationwide, we expected to find concentrations of schools where teachers were improving at every stage of their careers, or evidence that particular supports were especially helpful in boosting teachers' growth. After an exhaustive search, we were disappointed not to find what we hoped we would. Instead, what we found challenged our assumptions.