Like other public workers, teachers typically receive high and compressed ratings that do little to differentiate them based on performance. Motivated by empirical evidence of substantial variation in effectiveness among teachers, there has been a recent push to develop more informative evaluation systems with greater ratings dispersion. We study one of the first of these new systems, implemented in Tennessee, in order to understand how teachers respond to the provision of new, more differentiated performance ratings. We focus on whether summative ratings influence teachers' self-reported, self-directed professional improvement activities as measured by four items on a statewide teacher survey. Using a regression discontinuity design we find no evidence that teachers alter their time investments in professional improvement, or adjust their professional improvement activities based on evaluation feedback, in response to their ratings.