Outside the metropolitan Montreal area, bi/plurilingual secondary school students are most often integrated into a regular class as soon as they arrive at a French-language school in Quebec (De Koninck & Armand, 2012). Linguistic support services are then offered to help them with the twofold task of learning French, the language of instruction, and the subject content. To meet this challenge, these students, who have a plurilingual repertoire that can be used as a resource in the classroom (Cummins, 2021), need to develop their vocabulary in French, and more specifically their academic vocabulary, which is central to disciplinary learning (Short & Echevarría, 2016). The action research presented here therefore aimed to answer the following question: How can we promote the teaching and learning of academic vocabulary in linguistic support services, at the high school level, while building on students' plurilingual repertoires? To answer this question, we first drew up a portrait of teachers' needs in this area. Based on these needs, three activities were then designed and tested with three groups of students. Semi-structured interviews with the three teachers of the groups of students who took part in the study revealed the potential of the activities tested and suggested ways of improving them.