The Lawson Classroom Test of Scientific Reasoning (LCTSR) was used to gauge the relative effectiveness of three different methods of pedagogy, "Reading, Presenting, and Questioning" (RPQ), "Experimenting and Discussion" (ED), and "Traditional Methods" (TM), on increasing students' level of scientific thinking. The data of a one-semester-long senior high-school project indicate that, for the LCTSR: (a) the RPQ group (n = 91) achieved effect-sizes d = 0.30 and (b) the ED group (n = 85) attained effect-sizes d = 0.64. These methods have shown that the Piagetian and Vygotskian visions on learning and teaching can go hand in hand and as such achieve respectable results. To do so, it is important to challenge the students and thus encourage the shift towards higher levels of reasoning. This aim is facilitated through class management which recognizes the importance of collaborative learning. Carrying out Vygotsky's original intention to use teaching to promote cognitive development as well as subject concepts, this research has shown that it is better to have students experience cognitive conflict from directly observed experiments than by reflecting on reported experience from popularization papers or writings found on the internet. (Contains 4 tables and 1 note.)