Benedicte EstermanThis study proposes to look at the nature of language required in a middle school mathematics classroom through a teaching experiment. The teaching intervention proposes to provide explicit teaching of the mathematical and non-mathematical language and orchestrate subsequent opportunities for students to engage in substantive communication through cooperative groupwork. The emphasis will be on conceptual understanding through language acquisition rather than solely through learning procedures. The study proposes to examine the impact of the teaching intervention on student motivation and engagement in mathematics.