This study described the School-based Training Program (SBTP) and the performance of school administrators, science teachers, and students. The data were obtained from the 36 secondary school administrators, 127 science teacher SBTP participants, and students of the teacher participants. The data sources used were the Performance Appraisal System for School Administrators (PASSA) rating, the Performance Appraisal System for Teachers (PAST) rating, and students’ MPS result in science in the Division Achievement Test (DAT)/ Year- End Assessment Test (YEAT) for school years 2005 and 2008. Descriptive statistics employed were mean and standard deviation. The t-test for dependent samples was used to determine the differences among school administrators and science teachers’ performance, and t-test for independent samples was used for students’ performance before and after the implementation of the School- based Training Program. The .05 alpha level was used as the criterion for the acceptance or rejection of the null hypothesis. The study found out that the school administrators’ performance shifted from” very satisfactory” before the implementation to “ outstanding” after the implementation of the SBTP. This revealed an increase in their performance after attending the program. School-based Training program influenced the school administrators’ management role in curriculum and instruction supervision. Teachers’ performance was “very satisfactory” with a positive improvement noticed before and after the implementation of the program. School- based training program was a unique trend of teacher training which developed teachers’ instructional competencies. There was also a slight change in students’ performance which was “satisfactory” before and after the implementation of the SBTP. This can be explained by the fact that students were from different school years and with different backgrounds. The implementation of the School-based Training Program revealed statistically significant influence on school administrators’ and teachers’ performance. There was no significant difference in students’ performance before and after the implementation of the School-based Training Program.