Schools that define themselves as "multilingual" often offer no outlet for pupils' first languages other than the playground and corridors.
Dina Mehmedbegovic, of the Institute of Education in London, interviewed heads, teachers, pupils and politicians about the value they attached to bilingualism. She found that politicians' opinions varied depending on which language was under discussion. She quotes a Conservative MP referring to the Welsh language as "a very good thing", but also saying: "It does not matter... if people speak Bengali or not."
By contrast, heads welcomed multiculturalism in principle, but not necessarily in practice. Ms Mehmedbegovic said: "The diversity of cultures was celebrated and promoted in a consistent way... while languages received a different treatment from school to school."
Teachers often saw multilingualism as a threat to day-to-day teaching. One interviewee said that promoting community languages was acceptable, but only "within the context of protecting the national curriculum".
Another head explained that multilingual lessons were too challenging for teachers.
Many heads classed their schools as multilingual on the basis that they had bilingual pupils on their roll, despite the fact that these other languages were rarely spoken in class. "Bilingual children are still seen... as a problem rather than a resource," said Ms Mehmedbegovic. "The existing skills in these languages go unrecognised, are under-deployed or dismissed as a problem."
She suggests that teachers should take greater risks, allowing children to use languages they do not understand. They could then focus on awareness of different languages, rather than proficiency in any single one: "The teacher becomes a facilitator... while bilingual child- ren... take their place as experts."