Teachers are widely acknowledged as indispensable in enabling learners to construct purposeful knowledge structures while engaging in carefully structured learning activities. However, many studies have reported that learners’ understanding and construction of scientific knowledge at the secondary school level is genuinely challenging, particularly when teachers hold misconceptions that act as barriers to effectively facilitating knowledge construction by learners. Although well-organised instructions from the teacher can support the learning process, instructional and learning theories from various theoretical perspectives have been developed to enhance the effectiveness of that process. The scope of this chapter is, however, limited to Gagné’s cognitive learning theory, which can guide the instructional processes as learners develop understanding and skills to solve problems associated with a system of ‘connected particles’. Gagne’s theory includes a set of cognitive activities divided into five taxonomies: verbal information, intellectual skills, motor skills, cognitive skills and attitude. In addition to these learning domains, Gagné emphasises nine events of instruction that encompass all three of Bloom’s domains of knowledge. The nine events of instruction include gaining attention, informing objectives, stimulating recall of prior knowledge, presenting the materials, providing guidance, eliciting performance, providing feedback, assessing performance and enhancing retention of concepts. This chapter outlines how an in-service secondary mathematics teacher operationalises Gagné’s theory in a simulated classroom environment during the peer-micro teaching course. Although the teacher planned and implemented her lesson guided by clear lesson objectives, it was observed that she did not manage to accomplish the interplay between the cognitive activities and the events of instruction. Teachers, teacher educators, and policymakers may find this chapter helpful in promoting the implementation of Gagné’s theory in classroom instruction. This study aims to provide practical strategies for teachers, teacher educators, and policymakers to enhance instructional practices by incorporating critical thinking, improving classroom learning outcomes, and addressing the difficulties associated with implementing Gagné’s theory in educational settings.