TO EVALUATE YEAR-ROUND SCHOOLS, POLK COUNTY, FLORIDA, SCHOOLS REQUESTED A STUDY OF THE LITERATURE ON YEAR-ROUND OPERATION OF PUBLIC SCHOOLS AND A NATIONWIDE SURVEY OF STATE DEPARTMENTS OF EDUCATION. NEW YORK, CALIFORNIA, AND FLORIDA WERE FOUND TO OPERATE SOME SCHOOLS ON A YEAR-ROUND BASIS. THREE OF SEVEN OUTLINED PLANS WERE SELECTED FOR SPECIAL ANALYSIS--REGULAR YEAR PLUS SUMMER ATTENDANCE, STAGGERED FOUR QUARTERS, AND THE TRIMESTER PLAN. UNDER THE QUARTER SYSTEM, A POLK COUNTY ELEMENTARY SCHOOL WOULD REQUIRE A MINIMUM OF 540 PUPILS TO OPERATE AT LOWER COST THAN THE PRESENT SYSTEM ALLOWS BECAUSE INSTRUCTIONAL SALARIES AMOUNT TO 80 PERCENT OF ALL CURRENT EDUCATIONAL EXPENSES IN POLK COUNTY. UNDER THE TRIMESTER SYSTEM, THE ELEMENTARY SCHOOL WOULD REQUIRE A MINIMUM OF 432 PUPILS TO OPERATE WITH A LOWER TOTAL INSTRUCTIONAL SALARIES COST. JUNIOR AND SENIOR HIGH SCHOOLS WOULD REQUIRE MORE TEACHERS AND HIGHER SALARIES FOR BOTH THE QUARTER AND TRIMESTER SYSTEMS BECAUSE THEY MUST OFFER A WIDE RANGE OF SUBJECTS REQUIRING A LARGER PROPORTIONATE TEACHING STAFF THAN ELEMENTARY SCHOOLS. OTHER COST DIFFERENTIALS INCLUDE ADMINISTRATION, PLANT OPERATION, AUXILIARY CHARGES, FIXED CHARGES, AND CAPITAL OUTLAY. SPECIAL PROBLEMS INCLUDE ADMINISTRATION, PLANT MAINTENANCE, TEACHER RECRUITMENT AND RETENTION, CURRICULUM DEVELOPMENT, PUPIL REASSIGNMENT, AND PUBLIC RELATIONS. PUBLIC REACTION FROM 4,210 RESPONDENTS (2,477 PARENTS, 487 TEACHERS, AND 1,246 STUDENTS) FAVORED THE REGULAR SCHOOL YEAR PLUS SUMMER PROGRAM OPERATED WITHOUT COST TO PARENTS BUT WITH ATTENDANCE COMPULSORY FOR STUDENTS NOT PROMOTED AND VOLUNTARY FOR OTHERS. AN EIGHTH PLAN PROVIDING 210 DAYS OF CONTINUOUS STUDY FOR ALL PUPILS IS RECOMMENDED AS THE BEST MEANS OF INCREASING THE EDUCATIONAL QUALITY LEVEL AND OBTAINING THE GREATEST AMOUNT OF EDUCATIONAL RETURN PER DOLLAR INVESTED IN THE PUBLIC SCHOOLS. (JK)