This study aimed to understand chemistry lesson plan design and teaching at secondary schools with 14 teachers and 282 students, grade 11, through Randomized Post-test Control Group Design, placed in each experimental and control group. The experimental group was taught using multifunctional approaches, social constructivism, and laboratory experimentations. The control group was taught using traditional methods and laboratory experimentations, focusing on concepts of acids, bases, and salts. Indicators such as lesson topic, objectives, activities, evaluations, and conclusions were thematically reviewed, while teaching categories such as lesson organisation, activities teaching, pedagogical approaches, collaborative learning, teacher- student interaction, instructional resources, and students' academic performance were quantitatively analysed. Descriptive statistics were used to obtain frequency per cent (%), weighted mean, and standard deviation. The finding shows that teachers were knowledgeable about designing a chemistry lesson even though they followed the same trajectory and were inadequately prepared. In addition, only pedagogical approaches and instructional resources were moderately utilised among the teaching categories. Further, students in the experimental group performed better academically, as measured by their mean difference (12.121), significant (t = 6.142, p =.000), which may be attributed to paradigm-shifting from teacher-centred to the students-centred, instructional resources, students’ ability, and motivation. Therefore, the current lesson plan design as a case study in the chemistry classroom implies that effective lesson plans and teaching can lead to better learning of core competencies in the Gambian context if they were to be monitored and improved extensively. However, a further study may be needed by comparing the difference between pre-test and post-test scores, as this will indicate a better measure