Purpose: The purpose of this paper is to develop the notion of collaborative practice from theoretical and empirical bases. Design/methodology/approach: The research analysed the concepts of collaboration, reflective practice and the primary task. It also examined the ways of working of 18 primary schools in Wales where the level of student attainment in national test scores was high, despite the pupils experiencing considerable social and economic disadvantage. Findings: From the conceptual analysis, we contend that established models of joint working accord insufficient significance to the work task and that reflective practice is essentially a social process, which requires a task focus to be successful. In the schools we studied, there was a particular way of working which we have called "collaborative practice". It contributed substantively to their success. Collaborative practice is highly developed and inclusive joint working on a clearly defined main task, or primary task, in a reflective way. There are thus three elements to collaborative practice: collaboration, reflective practice and focus on the primary task. All three elements must be present for collaborative practice to be successful. Originality/value: The collaborative practice model provides a straightforward framework for analysing work in schools. It also gives a secure foundation on which to base successful practice in educational institutions. The collaborative practice model therefore has implications for research and practice in educational settings, for the practice of educational leaders and managers, and for the professional development of those who work in schools. (Contains 1 table and 1 figure.)