THIS STUDY INVOLVED (1) THE MODIFICATION OF BIOLOGY CURRICULA FOR USE BY 35 TEACHERS AND 4,264 STUDENTS IN THE SAN ANTONIO HIGH SCHOOLS, (2) THE ORGANIZATION OF A SEMIMONTHLY INSERVICE TEACHER TRAINING PROGRAM, AND (3) A STATISTICAL EVALUATION OF THE PROGRAM BASED ON DATA COLLECTED FROM A SAMPLE GROUP OF NINE TEACHERS AND 579 STUDENTS. BIOLOGY STUDENTS WERE GROUPED INTO THREE ABILITY LEVELS, WITH THE AVERAGE GROUP USING THE UNMODIFIED BIOLOGICAL SCIENCES CURRICULUM STUDY (BSCS) YELLOW VERSION AND THE SLOW LEARNER GROUP AND THE ACCELERATED GROUP USING MODIFIED CURRICULA. THE EXPERIMENTAL DESIGN PROVIDED FOR SOME CLASSES IN EACH OF THE LOW AND HIGH ABILITY GROUPS TO BE TAUGHT THE UNMODIFIED MATERIAL. DATA INDICATED (1) GAINS IN LEARNING WERE SIGNIFICANT AT THE .01 LEVEL FOR ALL GROUPS, (2) GAINS IN LEARNING FOR GROUPS USING UNMODIFIED MATERIALS WERE SIGNIFICANTLY GREATER FOR THE AVERAGE STUDENTS THAN FOR EITHER SLOW LEARNER OR ACCELERATED GROUPS, INDICATING THAT MODIFICATIONS WERE DESIRABLE FOR SLOW LEARNERS AND ACCELERATED STUDENTS, (3) DIFFERENCES IN BIOLOGY ACHIEVEMENT BETWEEN GROUPS USING THE UNMODIFIED CURRICULUM AND GROUPS USING MODIFIED CURRICULA WERE NOT SIGNIFICANT, (4) SIGNIFICANT DIFFERENCES WERE FOUND IN TEACHER-CLASS INTERACTION AMONG CLASSES WITHIN EACH OF THE GROUPS, AND (5) NO SIGNIFICANT DIFFERENCES WERE FOUND IN TEACHER-CLASS INTERACTION BETWEEN PAIRED EXPERIMENTAL AND CONTROL GROUPS. THIS DOCUMENT IS AVAILABLE AS ORDER NUMBER 67-3249 FOR $3.00 ON MICROFILM, $8.60 XEROGRAPHY, FROM UNIVERSITY MICROFILMS, 300 NORTH ZEEB ROAD, ANN ARBOR, MICHIGAN 48103. (DS)