This document explores the various aspects of the 45-15 plan of school operation, whereby four groups of students are in school 45 days and then off 15 days on a rotating schedule throughout the year. The publication overviews the general aspects of 45-15, considering the basic concept and its origin, general implementation, how the plan compares with other year-round school calendars, and its efficiency and flexibility. The implications of 45-15 on curriculum, community, students, teachers, finance, and legislation are discussed. Student evaluation under the 45-15 plan is considered, and sample progress reports are included. The document outlines the 45-15 scheduling procedure and the multiple access scheduling; including discussions on establishing the course catalog, student and teacher assignments, calendar selection, the scheduling process, and student transportation. (Author/DN)