CO-LAB meets a growing need in Europe to develop policy measures and practical initiatives to support large-scale, sustainable and effective practices in collaborative teaching and learning in schools. The ability to work together rather than individually to reach common goals or solve problems is a transversal skill which also has the potential to increase student motivation and longer term learning retention. Moreover, teacher collaboration within and across learning settings is increasingly part of the skill set expected of the modern teacher, but not yet widespread.CO-LAB brings together six ministries of education and national agencies working with both policy makers and schools, coordinated by EUN, to build the capacity of practitioners and policy makers in implementing collaborative practice at classroom and system levels.Scenarios to implement and assess collaborative student learning, an online course about collaborative practice, a community of practice and discussion workshops bringing together practitioners and policy-makers are the project’s pillars aiming at identifying the conditions needed at system level to support collaborative student learning and its assessment.Outputs of the project include innovative scenarios for collaborative learning and assessment, an online OER course for teachers, country reports and a cross-country evaluation of the impact of the initiative.To maximize impact CO-LAB will produce a range of highly engaging dissemination materials, tailored for specific target groups: policy makers, school leaders, teachers and teacher trainers. CO-LAB ambassadors will act as national champions for the results and there will be a closing conference session to present the outcomes, products and recommendations. The expected impact is more collaborative teaching and learning in schools, supported by changes in national regulatory frameworks, a set of collaborative learning scenarios and an online professional development course.