This study was designed to find out the possible ways to promote Activity-Based Learning (ABL) in Lower Secondary Science Classes (LSSC) in Government schools and was conducted in one of IED's cooperating Government Schools in Karachi with two science teachers in classes six and eight. Data were collected through a series of tests and reflections with students and teachers, personal reflections of the researcher, and discussions with all those directly involved in the study. Teachers also responded to relevant questions at the end of the study. The study was completed in three stages: Pre-intervention, Intervention and Post intervention. During the pre-intervention stage, I interviewed teachers, and observed their classes to assess the current practice of science teaching through Activity Based Learning and the difference between teachers' beliefs and practice. Another purpose was to attempt to assess the effect of current teaching practice on students' learning. The Transmission Mode of Teaching (TMT) was found to be the dominant style at this stage to promote learning. During the intervention stage, I facilitated the teachers in their efforts to apply ABL in their classrooms. It was discovered that ABL played an important role in promoting students' better conceptual understanding of the concepts covered. In addition, there were indications that the teachers' content and pedagogical knowledge improved. Though there were several major constraints faced by the teachers, it was felt that these factors could be partly circumvented with sound management. During evaluation of the teacher at the post-intervention stage, data concerning the amount of learning, the process followed, and the constraints faced during teaching and implementation were collected. Practical (ABL) work was seen to have had considerable impact on students' understanding of the concepts. Through this study I have come to know that though there are major constraints in applying ABL at the LSSC level, with proper classroom management and planning effective implementation of ABL is possible. The support given to the teacher by the administration is also an important factor.