Mathematics teaching usually occurs in a "public space"--e.g., a classroom is a public space with rules defining student and teacher roles that cultivate hierarchic relationships. Working in prison with young inmates (18-23 years old) from marginalized populations, we promoted alternative "common spaces" (physical and symbolic) challenging established hierarchies through equal contribution. Such mathematics curriculum employs an antideficit model (Louie et al., 2021) as prisoners co-research their lives with mathematics. Common spaces empower through recognition while enabling identity transformation. Qualitative data from the CoSpIRom [Common Spaces for Integration of Roma Project (http://cospirom.sed.uth.gr).] project explores: (a) whether common spaces, recognition and equal participation can support mathematics literacy while empowering and emancipating young prisoners; and (b) if and how this framework might prepare prospective teachers within contemporary diversity. Bringing together young prisoners and prospective teachers affects both populations. Mathematics curriculum developed through collaboration meets a consistent request from prisoners that educational programs bridge with the outside world as re-entry preparation. Contrasting life stories from prospective teachers operate as alternative models motivating prisoners to rethink their own life stories and self-concepts. Prospective teachers demonstrated significant intercultural communication skill development, empathy and solidarity for marginalized people, reporting important professional identity growth.