The Copernican Plan is a way to organize high schools on the basis of research and experience concerning more effective and efficient instruction. Research indicates that large-block scheduling has proven to be very successful. In the plan, each student will enroll in one class at a time for about 4 hours each day for a period of 30 days. An alternative is to enroll in two classes of about 2 hours each day for a trimester. Curriculum instruction and credits will be based on mastery of course objectives. A block of 60 to 70 minutes each day provides teachers and students additional time for extra help, study, and planning. In the afternoon students participate in seminars of approximately 70 minutes for credits that would be awarded on the basis of successful participation rather than on mastery or examinations. Five kinds of diplomas will be offered, each with different credit requirements. The Copernican Plan allows teachers to concentrate on the individual students rather than on whole classes. Additional requirements for each student are reliable attendance, reasonable conduct, and an individualized educational plan. Appended are 11 notes. (MLF)