Scientific literacy can be promoted through oral and written argumentative practice. Collaborative discourse has proven effective in fostering conceptual understanding, especially when discussions are developed under deliberative goals. Likewise, writing tasks as argumentative syntheses stand out for its epistemic value and its contribution to constructive learning processes. However, there are no known educational interventions that have combined these two didactic activities to teach science. The objective of this research was to compare the impact of four intervention programs, based on deliberative dialogues and argumentative synthesis writing activities, on the learning of socio-scientific content. The four programs resulted from the combination of two instructional components (Explicit Instruction; Guide), while deliberative dialogues and argumentative syntheses were constant elements. We conducted a pre-post quasi-experimental study in which participated 151 Spanish third grade secondary school students. Socio-scientific learning was evaluated through a content test made up of open questions. The results showed all students progressed in their socio-scientific knowledge. Instructional practices did not have a direct effect on content learning. However, we observed an indirect effect of explicit instruction on learning socio-scientific content, through learning of argumentative synthesis writing. Besides, we found a positive relation between progression in synthesis writing and knowledge acquisition.