The effects of collective bargaining contracts on school administration and teacher-principal relations are neither as visible nor as far-reaching as has been believed. Interviews with 189 teachers and 100 administrators, conducted in 18 schools in six diverse districts in as many states, indicate that implementation of contract provisions varies according to their enforceability and their importance to teachers. Fully implemented provisions, dealing with job security, class size, and duty-free lunch periods, were both easily enforceable and highly significant to teachers. Some important teacher concerns, however, such as student discipline and adequate materials and facilities, could only be partially enforced. Finally, some provisions that were enforceable but not highly important to teachers were variably implemented. Teachers and principals either ignored, enforced, or informally renegotiated such provisions, which included teachers' use of preparation periods, supervisory duties outside class, and meeting length and frequency. Implementation of these provisions could vary from school to school even in the same district, depending on the principal's administrative style and relationship to the faculty. (Author/RW)