Bilingual children are a valuable resource and more should be done to support the learning and retention of dual languages, a report says.
Learning dual languages improves educational ability, the report says
Cilt, the centre for languages, said research showed that language learning enhanced educational attainment.
It cites a study which found that bilingual children were more likely to achieve better GCSE results.
More than one in eight of England's primary pupils speak a language other than English before starting school.
Cilt patron Sir Trevor McDonald said the UK had access to a diverse range of languages which could be of great benefit to the economy.
"Yet, 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," he said.
"Rather than thinking in terms of an 'English-only' culture, we should be promoting 'English plus'."
The report cites a PhD study of secondary school students from Portuguese backgrounds by Olga Barradas at Goldsmith University.
She found that those who had attended Portuguese classes were five times more likely to get five or more GCSEs at grades A*-C than those who had not been encouraged to develop their home language.
"Being able to speak two languages improves a child's ability to use and learn language in general," the report says.
"Children can learn about something in one language and talk about it in another, and this process helps them to understand the subject better."
Family relations were enhanced if the children could communicate well with grandparents and other family members, it said.
"The maintenance of these languages does not mean they will be less proficient in English, or that they will be less adapted to life in British society," it says.
'Language of the month'
Cilt says employers are increasingly recognising the advantage and good marketing sense of communicating in the language of their customers - 65 of the languages spoken by UK schoolchildren are also spoken by more than 10 million people worldwide.
Around the country, in Essex there are 24 language groups containing more than 50 speakers, including nearly 200 children who speak Shona, the native language of Zimbabwe.
In Peterborough, primary school pupils regularly learn Italian, Urdu and Punjabi.
Examples of best practice include Newbury Park Primary School in Ilford, Essex, where all pupils learn simple phrases from a "language of the month" chosen from one of the 44 languages spokesn by pupils.
New Cross Hospital in Wolverhampton has integrated Punjabi into its foundation year modern apprenticeship in health and social care.