A year-long study of 28 third-grade teachers yielded extensive data describing their classroom management practices. The seven most effective and the seven least effective teachers were compared to determine what dimensions of mangement discriminated between them. Teachers who qualified as "better managers" had a firm preconceived notion of acceptable student behaviors and fashioned their classroom structures in such a way as to actively discourage intolerable behaviors. They also exhibited superb task analysis and an expertise in coordinating teacher and student activities in the most efficient manner. The "less effective" managers appeared to suffer from the lack of a clear set of expectation regarding student behavior and student work level. They considered student activity primarily on the basis of discouraging refractory deportment and did not display an adequately aggressive disposition towards positive student involvement. Although analysis is incomplete, some working hypotheses about the differences between the two types of teacher-managers are presented. (LH)