EXAMINED WERE THE CLASSROOM PRACTICES AND TEACHING RATIONALE OF HIGH SCHOOL BIOLOGY TEACHERS USING VARIOUS CURRICULUM MATERIALS. THREE GROUPS (64 TEACHERS) WERE ORGANIZED. GROUP EB CONSISTED OF 22 TEACHERS WITH A MEAN OF FIVE YEARS EXPERIENCE IN USING BIOLOGICAL SCIENCES CURRICULUM STUDY (BSCS) MATERIALS. GROUP BB CONSISTED OF 21 EXPERIENCED TEACHERS WHO WERE USING BSCS MATERIALS FOR THE FIRST TIME. GROUP NB WAS COMPOSED OF 21 EXPERIENCED TEACHERS WHO WERE USING MATERIALS OTHER THAN BSCS. THE TEACHER'S CLASSROOM PRACTICES WERE DETERMINED THROUGH THE COMPLETION OF THE BIOLOGY CLASSROOM ACTIVITY CHECKLIST (BCAC) BY THE STUDENTS IN ONE OF EACH TEACHER'S CLASSES. THIS CHECKLIST CLASSIFIED A TEACHER'S PRACTICES ACCORDING TO THEIR CONFORMITY WITH PRACTICES WHICH CONTRIBUTE POSITIVELY TOWARD THE ATTAINMENT OF BSCS OBJECTIVES. INDICATED WERE THAT (1) THERE WAS A SIGNIFICANT RELATIONSHIP BETWEEN THE MEAN SCORES ASSIGNED TO EACH TEACHER ON THE CLASSROOM PORTION AND THE LABORATORY PORTION OF THE BCAC, (2) THERE WERE HIGHLY SIGNIFICANT DIFFERENCES IN THE BCAC MEAN SCORES OBTAINED IN THE THREE GROUPS OF CLASSROOMS, (3) THERE WAS A SIGNIFICANT RELATIONSHIP BETWEEN SCORES ON THE BCAC AND SCORES ON AN INSTRUMENT DESIGNED TO DETERMINE A STUDENT'S UNDERSTANDING OF THE NATURE OF THE SCIENTIFIC ENTERPRISE. THIS DOCUMENT IS AVAILABLE AS ORDER NUMBER 67-3309 FOR $3.00 ON MICROFILM, $5.20 XEROGRAPHY, FROM UNIVERSITY MICROFILMS, 300 NORTH ZEEB ROAD, ANN ARBOR, MICHIGAN 48103. (DS)