Effects of observation duration on evaluations of teaching in secondary school band and choir rehearsals

The purpose of the present study was to determine whether expert evaluators' assessments of teachers vary between observations of rehearsal frames that demonstrate effective student behavior change and observations of full rehearsals. Ten experienced evaluators rated 12 music teachers on 10 criteria. The evaluators first observed brief video recordings of two rehearsal frames (RF) of each teacher and then a recording of a full rehearsal (FV) taught by the same teacher. The evaluators rated the teachers on all 10 criteria following each observation. Evaluators in the present study tended to rate teachers more highly and express greater confidence in their ratings in the FV condition than in the RF condition. These differences indicate that observing brief video episodes of teaching does not lead to the same ratings of teacher effectiveness as does observing video recordings of full rehearsals. The differences between the two conditions were larger in terms of evaluator confidence (29% higher confidence ratings in the FV condition) than in terms of ratings of teacher effectiveness (7% higher ratings in the FV condition). Although all teachers were rated more highly overall in the FV condition than in the RF condition, the differences between the two conditions were small and varied considerably among teachers and among evaluators.