This conceptual expression of "task interdependence," or role coupling, derived from research of elementary teachers in self-contained schools and team teaching schools, recommends that organizational theory provide clear concepts and measures to capture significant variations among schools. Research, measuring the independence-interdependence variable before and after team teaching implementation, sought a high degree of task interdependence. Autonomous personnel in a loosely coupled system were reorganized into collaborative work groups in a tightly coupled system. Researchers identified three types of task interdependence among teaching pairs: (1) resource interdependence--drawing on scarce resources; (2) throughput interdependence--depending upon another teacher to release pupils before the teacher can proceed; and (3) instructional interdependence--pursuing the same instructional activities and pupils. Instructional interdependence was measured because its intensity presupposedly increases with frequency of events, which imposes contingencies. Base information was obtained from daily teacher records of pupils and subjects taught. Observations indicate a loose coupling in the work system of team teaching schools; instructional interdependence is rare. Such characterizations of conventional schools as teacher isolation are over-drawn, for researchers found varying departures. Ironically, in contrasting conventional schools with team teaching schools, researchers discovered that what informants described was not, after measurement, so conventional. Stereotypes of the school's work system require replacement with useful categories by careful description and measurement. (CJH)