In German-speaking Central Switzerland, French used to be the only foreign language (FL) taught in primary schools (from Grade 5 onwards). According to the ongoing school reform, a second FL should be introduced in primary schools. Some cantons have now implemented a programme including English as the first FL to be learnt at school (from Grade 3 onwards), followed by French as the second FL (from Grade 5 onwards). To examine the impact of this school reform, children of both programmes (with and without previous English instruction) were compared with respect to their French competencies. During this 3-year longitudinal study (N = 928), children's listening and reading skills in English and French as well as their reading skills in German were assessed. After 1 year of French instruction, students with previous English instruction showed higher French listening and reading skills than students without previous FL learning experience. Both learners' English skills and their reading skills in the local language of instruction (German) exert a positive influence on the acquisition of the third language (French). A wide range of other contextual and individual factors were included in the analysis to examine if they contribute to the explanation of students' L3 skills. (Contains 2 figures, 4 tables, and 3 notes.)