From an enlarged conception of formative assessment and from the model of assessment for learning, this article examines a specific form of classroom-based assessment, which is integrated in students’ learning activities. This form of assessment is designed as an “interactive regulation-assessment” and a guided participation, whose function is to scaffold student’s self-regulation. However, this form of assessment should not be taken as any form of interactive assessment. The article presents a collaborative research carried out with nine teachers working in primary education in the canton of Geneva and having questions about how intervening in complex situations in order to support students’ learning. The results show four structures of guided participation that characterize dialogical processes of interactive regulation-assessment. In order to exemplify how leaning stakes are treated in these processes, the results focus on a specific problem in mathematics education, “Enclos de la chèvre”, taken from official textbook of French-speaking part of Switzerland.