We present the first results of the OPEN-MATH project that aims at the accomplishment of inclusive mathematics learning environments via the construction of the Open Activity Theory Lesson Plan (OATLP). We built a theoretical framework for inclusion that stems from the networking of differentiation for all, featured as open learning and the theory of objectification. We describe the interplay between theory and practice. Its outcome is a conceptual framework for inclusive mathematics and the development of the OATLP model across 3 implementations involving an Italian middle school class.