Despite the rhetoric of the Strategic Framework for European Cooperation in Education and Training (ET2020) to prison education – in particular, the learning needs of people excluded from policy and the recent research that emphasizes the crucial role of education for young prisoners’ personal development, and for their rehabilitation reducing the chances of recidivism (e.g., Jonck et al., 2015) in the Greek context, it seems that educational policies do not meet young prisoners’ educational needs (Petsas, 2017). We report on a project that directly addressed the inappropriate curricula and texts, and teachers’ lack of preparation for this population’s needs. The project ACTinPRISON (https://actinprison.sed.uth.gr)[1] pursued empowerment of young prisoners by creating common spaces between “insiders” --young prisoners-- and “outsiders” –the academic team and students/prospective teachers. Our “common spaces” framework mitigated the dominant, disciplinary, prison discourse with the perspective and techniques of Critical Communicative Methodology (CCM) for developing mathematics and language literacy. This challenged symbolic boundaries separating the two groups by using co-creation of mathematics to foster equal participation and interaction. The initial needs analysis phase of the project introduced young prisoners to the idea and practice of research as a matter of participatory practice, and incorporated important mathematics concepts and skills within jointly constructed community-building activities. Likewise, moments of open-ended discussion were effective as emergent language and mathematical literacy events The second project phase applied that experience to the preparation of university students for entering the prison, followed by the university students and young prisoners working together in the common spaces inside prison. Again, mathematical activities evolved as extensions of the information regarding their funds of knowledge. Work sometimes integrated this knowledge into theatrical play, at other times the group exploited mathematics contexts as here-and-now moments of group development. These experiences afforded the expression of situated mathematical concepts through informal mathematical language as the young prisoners were exposed to the idea of a mathematics register. We report on our persistent pursuit of a transition to scientific language use in this educational context despite the complexity of this challenge. (Resource limitations combined with super-diverse sociolinguistic repertoires and literacy backgrounds of the participants were treated as opportunities rather than obstacles). The ACTinPRISON project extends previous action creating common spaces with young prisoners and prospective teachers (http://cospirom.sed.uth.gr) that identified the need for new participatory practices to challenge typical research protocols. This new work responds through joint mathematically-rich activity to post-colonial critiques of research with marginalized populations. Such critiques often describe research as a “dirty word” (Thambinathan & Kinsella, 2021), because it perpetuates forms of hierarchy and injustice. We counteracted this concern by inviting young prisoners to be co-researchers of their experiences. The examples we present here result from bottom-up extra-curricular experiences involving mathematical ideas. We discuss how such an atypical “school framework” challenges together numerous expectations of both traditional mathematics education and commonsense discourse of prison life. Based on this project experience, we propose in our conclusion the potential for co-constructed needs analysis research to set the stage for informed curriculum development when working with disenfranchised learners who research their own needs. We also discuss the challenges of making this kind of work sustainable and institutionalized.