Interactive Groups (IG) are defined as a way of class organization. IG are small groups of students, heterogeneous in terms of learning attainment, cultural origin, gender, etc. IG works under a dialogical approach. An adult, who may be a parent, a member of the community or any other person involved as volunteer, animates each group. The key of success of this approach is the interaction among students and adults. In this paper we analyse the case of an elementary school with a high rate of diversity , placed in a city in the metropolitan area of Barcelona. The Critical Communicative Methodology (CCM) is used to analyse the data collected, using field notes (classroom observations) and videotaped sessions. We discuss how a classroom of 6th graders deals with problem-solving, division, and place value activities, using IG. Teacher, students and other members of the community involved in the teaching and learning of mathematics explain the emergence of community knowledge (funds of knowledge) that enriches mathematics learning. We conclude that egalitarian dialogue promoted in the IG incentives rich mathematics interactions, which improve students’ understanding and achievement in mathematics.