Bilingual children who learn in their family's language as well as English do better at school, research suggests.
Being bilingual can be seen as a hurdle children have to overcome
Even second and third generation immigrant children with English as their stronger language could benefit.
A team from Goldsmiths, University of London, analysed some primary school children in England using two languages in maths and English lessons.
They found that, far from confusing them, having two languages deepened their understanding of key concepts.
Lead researcher Dr Charmian Kenner said children who led bilingual lives could access their lessons through both languages.
"Learning a mathematical concept in Bengali and English, for example, deepens understanding as ideas are transferred between languages.
"Or children can compare how metaphors are constructed in a Bengali poem and its English equivalent.
"The children in our project expressed a strong desire to use their community language in school and teachers were able to tap into their pupils' full range of cultural knowledge."
Dr Kenner worked with four small groups of children aged between six and 10 at two primary schools in the London Borough of Tower Hamlets.
She watched them learning their mother tongue in community language classes, after school or at weekends, and observed them in bilingual activities in mainstream classes.
When the children were allowed to use their mother tongue as well as English they seemed to grasp mathematical concepts such as division and multiplication more easily, she said.
A separate research project carried out by Tower Hamlets community language unit found children who attended mother tongue classes did better in their national curriculum tests.
Schools which have a high proportion of children with English as a second language are generally expected to do worse than those that do not.
But this research suggests that bilingual pupils do better than those with just one language.
Dr Kenner warns that many second and third generation children are in danger of losing their bilingual skills if they do not have the chance to develop their mother tongue through their schoolwork.
She now wants multilingual children to be allowed to use their mother tongue in mainstream classes.
Her call comes soon after the government urged schools to ensure Britishness was at the heart of citizenship lessons.
The argument that classes should be only in English is based on assumptions that run contrary to all the research findings, Dr Kenner said.
"The other thing is that people think that, in order to be British, children of immigrants have to distort parts of their identity ... but we found it was the other way round.
"The children wanted to be able to use Bengali at school as it was part of them. For them being British included being Bangladeshi. They are British Bangladeshi."
The Department for Education and Skills has recently funded a research project aimed at spreading best practice from bilingual schools.
Dr Kenner said: "The advice has changed quite a lot. When the first wave of people arrived in the 1960s and 1970s people were told only to speak English to their children.
"But we can see that it is very important that parents continue to talk to their children in their first language and then they can transfer the key ideas they learn to their new language which would be English at school."
The findings come after the centre for languages, Cilt, found bilingual pupils do better at GCSE.
Cilt patron Sir Trevor McDonald said: "In our haste to ensure they acquire good English, we frequently miss the opportunity to ensure they maintain and develop their skills in their other languages too.
"Rather than thinking in terms of an 'English-only' culture, we should be promoting 'English plus'."