“…For example, Ronfeldt (2012Ronfeldt ( , 2015 finds that student teachers in schools with less teacher turnover, higher value added, and better teacher collaboration tend to be more effective once they enter the workforce. Bastian et al (2020); ; Matsko et al (2020); Ronfeldt, Brockman, and Campbell (2018); and Ronfeldt et al (2021) also connect the effectiveness of candidates' mentor teachers (i.e., the inservice teachers who supervise their student teaching placements) to the candidate's future feelings of preparedness (Matsko et al, 2020) and effectiveness; candidates who were mentored by teachers with higher evaluation scores (Bastian et al, 2020;Ronfeldt, Brockman, & Campbell, 2018;Ronfeldt et al, 2021) or higher value added (Bastian et al, 2020;Ronfeldt, Brockman, & Campbell, 2018) tend to be more effective according to these same measures once they enter the workforce. While all of these studies are subject to potential omitted-variable bias-for example, these findings could be explained by the nonrandom sorting of candidates to student teaching and first teaching positionstwo recent experimental studies (Ronfeldt et al, 2020;Ronfeldt, Goldhaber, et al, 2018) provide preliminary evidence that candidates randomly assigned to "better" student teacher placements according to these measures report better selfperceived preparedness than candidates randomly assigned to "worse" placements.…”