The growth in communities teaching their own languages in the UK should be seen as an educational asset, language experts have said.
Fewer pupils are studying language GSCEs but more communities are teaching their languages, say researchers.
More than 60 languages are being taught in communities, promoting bilingualism, says Cilt, the national centre for languages.
Schools offer 35 languages in the curriculum or after-school clubs.
A study for Cilt argues bilingualism should be more highly valued in Britain.
About one in 10 children speak a language other than English at home, researchers found.
The study reports the linguistic map of Britain is changing, with multi-lingualism spreading beyond typically multi-ethnic areas.
Children in England speak at least 300 different languages between them, the study showed.
More than 100 languages are now spoken in Scotland and nearly as many in Wales.
In Wrexham, an area which had very few community language speakers until recently, at least 25 languages are now in use, including Portuguese, Polish, Tagalog and Shona, the report said.
"Many of the benefits which modern languages specialists recognise in students who gain competence in languages, such as French, German or Spanish, apply equally to those who speak community languages, such as Urdu, Chinese or Greek," researchers said.
The report said bilingual students would share an interest in the wider world and a willingness to engage with people and ideas from elsewhere in the world.
Some community languages would become more and more useful in the business world, as globalisation continued, particularly Urdu, Turkish, Chinese, Bengali and Arabic.
Isabella Moore, the director of Cilt, said there was vast potential for harnessing the linguistic talents of pupils.
"This summer business leaders drew attention to our country's need for capability in a wider range of languages.
"Yet 9% of our secondary school children and over 10% of primary children already speak another language at home, and many more have one in their family background.
"By encouraging students to develop their existing knowledge we will be building up an important skills base, as well as raising educational achievement."
Joanna McPake, of Stirling University, led the study.
"There is a huge body of research testifying to the benefits of bilingualism for educational development. Yet our survey has shown that schools do not always appreciate the value of maintaining and developing language skills other than English," she said.
"In addition, both mainstream and complementary schools underestimate the practical value of other languages for students' future careers."