The MIXAP-EU (MIXed reality authoring APplications for and by teachers in EUrope) project builds a partnership of researchers and professionals to support in-service teachers in the creation of Mixed Reality (MR) activities for school education. It has three main objectives : providing insight on the best ways to use MR in schools, producing an open-source authoring tool that allows teachers to create custom MR activities and bringing together a supportive international community of teachers.