This article evaluates whether providing coaching between practice sessions in teacher education courses leads to more rapid development of skills and changes in teachers' beliefs about student behavior, using mixed-reality simulations as a practice space and standardized assessment platform. We randomly assigned 105 prospective teachers to different coaching conditions between simulation sessions integrated into a teacher preparation program. Coached candidates had significant and large improvements on skills relative to those who only reflected on their teaching. We also observe significant coaching effects on candidates' perceptions of student behavior and ideas about next steps for addressing perceived behavioral issues. Findings suggest that skills with which novices struggle can improve with coaching and do not have to be learned "on the job."