Learner-centred methods of teaching are rarely used in most Nigerian classrooms. Pedagogic practices at the basic level of education encourage teacher-dominated methods that do not allow for students’ active participation and inculcation of behavioural changes that reflect the outcomes of learning Social studies. As a paradigm shift, the main effects of treatments (Self-directed learning, Collaborative task method and a combination of the two methods), gender and achievement motivation on the combined dependent variables of achievement in Social studies and critical thinking were investigated. Three hypotheses stated were tested at the 0.05 level of significance. A pre-test post-test non-randomised control group design was adopted in which treatments were crossed with two levels of achievement motivation and gender respectively. 223 males and 136 female students were randomly selected from 12 junior secondary schools in Oyo State. Three instruments: Academic Achievement Motivation Inventory (α = 0.83), Critical Thinking Disposition Inventory (α = 0.87) and Social Studies Achievement Test (r = 0.80) were used to collect data from the participants. Using Multivariate Analysis of Covariance (MANCOVA), Self-directed learning proved to be most significant in improving the learning of Social studies concepts, followed by a combination of Self-directed learning and Collaborative task methods while the Collaborative task method was the least effective. Gender and achievement motivation had significant effects on students’ achievement and not on critical thinking. The findings have implications for the teaching of Social studies in Nigeria. If the rationale of instruction is to enhance the acquisition of cognitive learning outcome with the teacher acting as a facilitator, then the Self-directed learning is most beneficial to students followed by a combination of Self-directed learning and Collaborative task method. When students are actively involved in the teaching-learning process, their academic achievement is more enhanced, especially when a conducive environment is provided.