The astonishing demands placed on Britain's biggest primary school by the surge in immigration will be laid bare this week.

A fly-on-the-wall television documentary reveals that in 1997 at Gascoigne Primary School in Barking, East London, 90 per cent of pupils spoke English as their first language. That figure has now fallen to ten per cent.

More than 60 different languages are spoken by the youngsters, according to the four-part series.

The documentary shows foreign children struggling to cope because they do not speak English, while teachers and even other pupils devote time during lessons to helping them.

More than 60 different languages are spoken by the youngsters at Gascoigne Primary School in London

In one scene, a ten-year-old from Bulgaria cannot answer a question about how old he is. In another, a seven-year-old boy from Portugal who arrives speaking no English has to sit with other Portuguese-speaking pupils who act as translators.

The number of pupils aged between five and 11 at the sprawling site has jumped from 700 to more than 1,100 since head teacher Bob Garton arrived eight years ago.

There is a massive turnover of children, with about ten leaving each week to be replaced by newcomers.

About 300 boys and girls a year arrive during term-time rather than at the start of the year – five times more than the national average.

More than a third of new arrivals at Gascoigne speak no English and others do not have it as their main language at home.

A fly-on-the-wall television documentary has revealed that in 1997, 90 per cent of pupils spoke English as their first language, pictured is a school photo from the 1970s

Critics warn that the focus put on non-English speakers 'must have an impact' on the education of English speakers.

Education expert Professor Alan Smithers, who grew up in the Barking and Dagenham area, said: 'The growing gap between white working-class pupils and those from more prosperous backgrounds, which is of great concern to the Government, won't be narrowed if foreign-born pupils dominate an increasing number of our primary schools.'

Prof Smithers, director of the Centre for Education and Employment Research at Buckingham University, added: 'I wonder if this massive school with a huge turnover and non-English speakers is giving children the start I was able to enjoy in my relatively small, working-class primary?'

In the Channel 5 documentary, Britain's Biggest Primary School, which starts on Thursday, a bewildered boy, Edson, is shown being introduced to his new class.

The teacher says: 'Edson is from Portugal. Hands up who started at this school and did not speak English when they came first?' Of about 20 pupils shown, the majority raise their hands. The teacher then tells Edson to sit with a group of girls, explaining: 'They all speak Portuguese, so you're going to sit beside Luenna today. Is that OK?'

More than a third of new arrivals at Gascoigne Primary (pictured) in Barking, East London, speak no English

In another scene, Viktor from Bulgaria is asked by the programme makers: 'How old are you?' He says: 'Erm…' Again asked his age, he says: 'Erm… I'm…'

Both boys are shown later in the series having significantly improved their grasp of the language with help from English as an additional language (EAL) teachers and support assistants.

Mr Garton tells the documentary team there is 'a sort of three-way split of backgrounds' throughout the school – a third are Eastern European, mainly Albanian-Kosovan, a third are of African origin, and a third are from the Indian subcontinent, with a 'tiny percentage' of white British children.

Some parents speak warmly of the school and maintain the language barriers present no problems for their children's education.

Sarah Mallia, who is British-born but married to an Albanian, says her daughter Melissa, five, speaks English and Albanian.

'When they have had children arriving who don't speak any English, I know Melissa has taken them under her wing and helped them settle in,' she says.

Afsheen Amir says her daughter Abia, six, loves the school. 'There are a lot of languages spoken, but the teachers and the other children seem to cope very well with that.'

The school has been rated 'good' by education watchdog Ofsted. However, its results in national tests for 11-year-olds are below the national average.