The project is a randomized controlled trial of the effect of teacher training on student's language abilities. The overall aim is to provide first–class language and communication teaching for all students by creating communication fostering classroom environments in the mainstream setting. We implement a collaborative learning intervention program, where speech language pathologists and mainstream primary school teachers collaborate. The novelty of our initiative lies in the evidence–based methodology to support both teachers' and students' communication skills using a randomized controlled trial design. There is today severe concern about how to provide equitable, efficient services and true inclusive education for the increasing number of children with weak language, in high risk of academic and social failure. Weak language can be the consequence of language impairment or other neurodevelopmental disorders, due to recent immigration or socioeconomic risk factors.