This case study describes an action research project aimed at improving the writing skills of disadvantaged background students and first-generation immigrants at the elementary-school level. This research was based on the hypothesis that poor writing skills may have negative effects on the academic outcomes for disadvantaged background students and first-generation immigrants. This limitation, in turn, would lead to a high dropout rate. Knowledge co-construction and differentiated instruction appeared to be interesting ways for teachers to improve the writing skills of students from the aforementioned backgrounds. We conducted collaborative action research with six elementary school teachers and 126 students. The research goals were achieved through an iterative research approach that entailed holding meetings for the purpose of knowledge co-construction and other various forms of collaboration (practices, activities of exploration of the relationship to the writing of students, co-development of practices rooted in the reality of the class, and taking into account the needs expressed by the students). This case study describes the way this research approach was implemented, illustrating the potential of action research in contributing to the empowerment of vulnerable school populations. Several practical questions are discussed: What are the ways to earn the trust of disadvantaged and minority communities as research participants? What research designs can specifically be tailored to the unique situations of these communities? How can we collect data in a way that is respectful to these communities while making research inclusive and empowering? [This content is provided in the format of an e-book.]