New studies show that the instructional effectiveness of preservice candidates and their cooperating teachers are positively related. However, we neither know if these relationships are causal nor, assuming they are, if it is possible to significantly increase the instructional effectiveness of the cooperating teacher pool. In this study, we randomly assign districts to receive recommendation lists (generated using administrative data) for the recruitment of more promising cooperating teachers. Districts receiving lists recruited significantly more effective/experienced cooperating teachers, while candidates placed in these districts felt significantly better prepared to teach. As a result, this study offers an innovative, low-cost strategy for recruiting effective/experienced cooperating teachers and presents the first causal estimates that more effective/experienced cooperating teachers improve candidates’ preparedness to teach.

Despite the critical role of mentors in the preparation of preservice teachers, very little causal quantitative research has explored the effects of offering mentors professional development (PD) around how to coach and support their candidates. We conduct an experimental evaluation of a PD opportunity randomly offered to mentors within six different Tennessee programs over the course of 3 years to investigate its impacts on the perceptions and practices of both the mentors themselves and their candidates. PD significantly increased the frequency of coaching provided by mentors and mentors’ own instructional effectiveness but did not impact their candidates’ satisfaction or feelings of preparedness, though candidates of mentors assigned to treatment were marginally significantly more likely to find employment.