This paper assesses the potential of coaches to provide objective and valid ratings of teacher-child interactions. The study examines the association between a coach-ratings measure, the Teacher Knowledge and Skills Scale (TKSS), and the Classroom Assessment Scoring System (CLASS), an observational measure that has been found to be a valid assessment of teacher-child interactions. The study also examines the association between one possible source of bias, the coach-teacher relationship, and the coaches' ratings of teacher-child interactions. A sample of 152 early childhood teachers and 12 coaches implementing a coaching intervention participated in this study. Results show a strong correspondence between coaches' and observers' ratings of teacher-child interactions, as well as a tendency for coaches to rate teachers with whom they have higher-quality relationships more favorably. The paper discusses possible ways in which the coaches' ratings can be improved and used to have a more reliable, cost-effective way to assess teacher-child interactions. (author abstract)