Concept 6, a new program designed to cope with burgeoning enrollments and a shortage of classroom space in Jefferson County, Colorado, keeps school buildings in use 250 days and divides the school year into six terms of instruction. Individual students attend classes four terms and choose their vacations during the other two. An option for a fifth term is available to those who choose it for enrichment, remediation, or acceleration at no expense. Teachers work the normal 184-day work year, but may choose to teach 225 days when enrollments make it possible. The plan has the effect of producing up to 50 percent more classroom space. A key feature in making Concept 6 desirable to students is the voluntary vacation choice. As many as one-third of the students enrolled may be on vacation at a time. The program should lead to greater individualization of instruction and to a broader range of curricular activities in individual schools. Throughout the district, 80 percent of the parents of school age children and 79 percent of the staff favor the plan. The participation of parents, students, and school staff members on advisory committees should facilitate a smooth, trouble-free transition to the year-round school calendar. (Author/DN)