Abstract
Abstract The present quasi-experimental study explores the effects of instruction on secondary students’ scientific argumentative writing in a Basque medium of instruction program. Secondary students ( N = 105) completed written tasks before and after a unit on energy in their science class as part of this investigation. The experimental group ( n = 61) additionally took part in three, one-hour sessions focused on scientific argumentation via instruction in cognitive discourse functions ( Dalton-Puffer, 2013 ), while the control group ( n = 44) completed the unit on energy without the additional instruction on argumentation. The final corpus of 210 texts was analysed using Toulmin’s Argumentation Pattern ( 1958 ). ANOVAs showed that the experimental group’s use of argumentation strategies increased significantly, while the control group’s use of such strategies did not increase. Thus, the results show that instruction on argumentation helps students to write better argumentative compositions. These findings suggest that instruction in the use of Cognitive Discourse Functions allows for academic language learning in bilingual education contexts. The pedagogical implications and future research directions of this study’s findings are discussed.