The numbers of children at primary school are expected to rise by a fifth over the coming decade, official figures suggest, putting huge pressure on primary schools to cater to demand.
By 2020, there will be 4.8 million state primary pupils - 20% higher than in 2011 and reaching levels last seen in the early 1970s, according to statistics published by the Department for Education (DfE).
The hike is being fuelled by a birth rate that has been rising since 2002, and is projected to continue to increase until 2014, the data suggests.
By 2015 there will be 4.39 million primary age children in England, a 10% increase from last year.
The rise in pupil numbers is set to put more pressure on school places, which are already being severely stretched in some parts of the country.
Figures published earlier this month showed that a fifth of primary schools and a quarter of secondaries were full or had too many pupils last year.
In total, more than 4,000 schools across England were at or above the limit in terms of student numbers - with Bristol and parts of London among those feeling the squeeze the most.
Tuesday's statistics, looking at national pupil projections, show that while primary numbers are set to increase, secondary school pupil numbers are set to fall.
The data shows that state-funded secondary school pupils aged under 16 reached a peak in 2004, and then began falling.
In 2011, there were 2.84 million state-funded secondary pupils aged under 16.
This is expected to fall by around 5% to 2.7 million by 2015, and then start to rise again as primary school pupils start secondary school.
Schools Minister Lord Hill said: "We're creating thousands more places to deal with the impact of soaring birth rates on primary schools. We're more than doubling targeted investment at areas facing the greatest pressure on numbers - over £4billion in the next four years.
"We are building Free Schools and letting the most popular schools expand to meet demand from parents. We are intervening to drive up standards in the weakest schools with thousands of empty places nationally - so they become places where parents actually want to send their children."
Shadow education secretary Stephen Twigg said: "The analysis of future pupil numbers shows the Government must respond to real need in our education system, not just promote pet projects.
"There is an urgent crisis in our primary school system that the Government is ignoring - 10% more places are needed before the election. By contrast, secondary school numbers are expected to be 5% lower than in 2011.
"The majority of need is for primaries yet half the funding from the Autumn Statement will go on pet projects like free schools.
Only a third of free schools in the pipeline are primaries, and the areas with the biggest need will not get a free school. This shows how out of touch the Tory-led Government is with real need on the ground.
"At a time of budget constraints, and with many parents struggling to get into their first choice primary school, these figures should be a wake-up call to the Government."
Sir Andrew Green, chairman of the campaign group Migration Watch UK, said: "This is a clear result of Labour's mass immigration policy and will put huge strain on our primary schools.
"Last year a quarter of all births were to foreign-born mothers who, on average, have 30% more children than British women.
"These new figures show why we must cut back immigration very sharply if we are to slow down the rapid increase in our population, of which two thirds is due to immigration."