Research experience for 13 years are based on improving secondary school students' achievement and interest in science especially chemistry through teaching method. A study of the developmental process and how learners encode knowledge in memory after conceptual understanding and active participation as very essential elements in the learning process has over the years been addressed. The importance of learners' becoming critical thinkers and owning responsibility of learning process are underscored. This was intended also to ensure that gender gap in science and technology is bridged as achievement in science for both boys and girls are key drivers to the nations' development