School boards can improve their schools if they focus on four factors that educational research says most strongly influence school effectiveness. The four factors are (1) the time students spend on the subject matter each day, (2) textbooks, (3) teachers and their teaching methods, and (4) principals' support to help teachers achieve instructional objectives. For each factor, board policies can help improve effectiveness. Concerning the factor of time, for instance, board policies should allot specific amounts of time to basic skills instruction, require daily lesson plans, and discourage classroom interruptions and time not spent on instruction. A board should require textbooks to match its policies on educational philosophy and teaching methods and should make sure textbooks are readable and appropriate to the grade level. For teachers, boards should set specific hiring standards and instructional strategies and should prescribe regular formal evaluations and additional inservice training where improvement is needed. Finally, boards should specify principals' tasks and encourage them to concentrate on teacher evaluation and classroom supervision. (Author/RW)