Pupils who speak English as an additional language in England could have their extra language help limited to three to five years.
Putting a time limit on such support is one of the options the government is exploring, after a consultation on school funding.
One in six pupils in England's state primary schools speaks English as an additional language.
The government says no decisions have yet been made.
It says it is "well aware" of the need for children to learn English but that most achieve this long before they are 16.
The proportion of pupils in England with English as an Additional Language (EAL) increased from 16% in January 2010 to 16.8% in January 2011, according to the school census.
In April 2011, an Ethnic Minority Achievement grant given to schools to help them provide English language lessons was merged into the overall school budget, rather than remaining an individual grant for specific purposes, as were other grants.
And in a consultation document published last summer, one of the questions asked was whether funding for English as an Additional Language should be limited to between three and five years up the age of 16.
The National Association for Language Development in the curriculum (Naldic) is worried that funding for these pupils is no longer ring-fenced.
Frank Monaghan, the vice chair of Naldic, wants the government to provide EAL funding for a minimum of five to seven years.
"What we know is that students who have English as an additional language have very distinctive needs," he said.
Bilingual primary school children in Slough Slough pupils Tayiba and Hassam, aged five, speak Urdu, while Alaap, also aged five, speaks Gujarati
"They need to be dealt with by people who are experts in language and second language development. If they don't get that, they are unlikely to make the kind of progress that we would want them to make, and they are able to make."
At present there is no specific cut-off point for EAL funding. Some pupils need extra help for a number of weeks, while others need support for a few years.
Mr Monaghan says schools and Naldic have seen the benefits of these lessons.
"It is a great worry for the gains that have been made, and we have seen the gap in attainment, particularly amongst Asian groups, narrowing," he said.
"The Bangladeshi group, which was once under-performing, has been catching up where we have had the targeted interventions."
At the moment the government is talking about narrowing the gap, and it is looking at severe deprivation. But language is narrowing the gap”
End Quote Charlie McGeachie Head Teacher, Montem Primary School, Slough
The number of ethnic minority children in schools in England has increased by 57% over the past decade.
In Slough, 56% of primary school children have a first language that is not English.
At Montem Primary School, an estimated 70% of pupils are bilingual. Many children speak Urdu, Punjabi, Romanian, Polish, Albanian and Gujarati.
Head teacher Charlie McGeachie says that the challenge is to make sure that children understand English.
"For many of them, English will be a second language. Therefore that is our primary cause, when we do the curriculum, we have to make sure we are set up to support language development," he said.
"A school's job is to make sure that every child is given a catch up. At the moment the government is talking about narrowing the gap, and it is looking at severe deprivation. But language is narrowing the gap."
At this school 96% of pupils are from ethnic minority backgrounds.
Shafi Ahmed works as an Ethnic Minority Achievement teacher for years 3 and 4 (seven to nine-year-olds).
"It is very important for people to have their mother language as well as English," she said.
"We don't say to parents 'Don't speak the language to them at home', because they need the language and English. We work in their home language which is very important for their identity," she said.
A Department for Education spokeswoman said: "In the consultation published in July we included a number of options for future handling of English as an Additional Language. We are considering the responses to the consultation and have not reached any conclusions.
"We are very much aware of the need for support for children who do not speak English fluently, but we are also aware that many children who speak another language at home come to be fluent in English well before the end of 11 years in school, so that it is not necessary to continue additional support at that stage."
She added that children joining a school with English as a second language at any age up to 16 would be eligible for such support under the proposals.