Year round school programs are more difficult to implement in secondary schools because of the nature of teaching and the seasonal organization of extracurricular activities in high schools. There is no one year round program that is desirable for all schools. When considering a year round program for the first time the following variables should be considered: (1) the number of attendance terms; (2) the number of vacation periods available in the calendar; (3) the number of holidays to observe; (4) the number of attendance tracks; and (5) the number of students released per vacation. A second set of factors to be considered are the stipulations placed upon the school calendar by the local school district. The year round program enacted by the Jefferson County (Colorado) system was a plan with six attendance terms (concept 6), offering each student two vacations during the year. Three year round school models (with a detailed analysis of the concept 6 plan) are presented from the study conducted by the Year Round School Study Committee of Jefferson County. The models are: (1) the four quarter year round high school schedule; (2) the five term year round high school schedule; and (3) the concept-6 year round program (six term year). An eight point list of "Do's and Dont's" to be considered when changing to year round high school schedules is also provided. (MD)