Primary teachers needed to cope with immigrant pupils now and 500,000 English-born in future.
Extra primary staff are being urgently recruited because of Eastern European immigration and rising birth rates. And university admissions officers have accused ministers of short-termism for cutting secondary training when the rise in population will affect the sector.
Jim Knight, schools minister, will review funding for teacher training next year in order to increase recruitment. He has already provided extra cash for schools with an influx of immigrant pupils, but ministers have not previously admitted the more pressing problem of the lack of teachers.
Projections from the Office for National Statistics show rising birth rates will mean an increase of half a million more English-born children in primary schools by 2015. But secondary trainee places are being cut by more than 1,200 per year over the next three years.
Now, ministers are having to increase primary training places by 600 a year. But as they make cuts to secondary training numbers, they know the new baby boom will hit secondaries in a few years' time.
To complicate matters further, previously falling rolls have been blamed for closure of small, rural primary schools: 219 with fewer than 100 pupils have shut since 1997. Protests have prompted Mr Knight to write to local authorities this week saying they must keep successful village schools open as a "top priority". Population figures show councils may be forced to reopen them when the next baby boom hits schools.
The Government cannot predict how many immigrant children will arrive in the coming years. It has underestimated immigrant numbers every year since Poland and seven other countries joined the European Union in 2004.
The Department for Children, Schools and Families, lacking confidence in official projections, will reassess pupil numbers in autumn 2009. "This three-year recruitment period will be affected by significant demographic changes," Mr Knight said in a letter to the Training and Development Agency for Schools (TDA).
James Rogers, executive director of the Universities' Council for the Education of Teachers, said ministers did not recognise the extent of the challenge. "The primary increases - though welcome to an extent - still don't take sufficient account of immigration or an upsurge in birth rates," he said.
Ramona Mitrea, 32, a teacher from Romania, will help fill the staffing gap and support the cultural and language needs of Eastern European pupils. She speaks four languages and is completing a PGCE in modern languages at Edge Hill University in Ormskirk.
At Byrchall High in Ashton-in-Makerfield, near Wigan, where she is on placement, she has a newly arrived Polish girl. Eastern European immigrants adapt quickly, she said.
"I was really upset last year when all the newspapers were saying that Romanians were invading England," she said. "I think most of the Romanians who come here, like me, have qualifications and some experience that allow them to contribute a lot to the community."
Mick Brookes, general secretary of the National Association of Head Teachers, has urged the Government to support poorly funded primaries that have had to cope with the sudden arrival of large numbers of immigrant pupils.
Stephen Watkins, headteacher of Mill Field Primary in Leeds, is often forced to rely on the school's building supervisor - a third-generation Polish immigrant - for translation. "You never know when new pupils are coming. They just land," he said.
More than a quarter of the school's 250 pupils are new immigrants from Poland, Slovakia, Singapore, Malaysia, Sudan and the Congo. The latest arrivals are six Czech children.
"These six Czech children will probably stay till June, then be rehoused," he said. "They come in, they don't speak English and some haven't been to school before, but they're very hard-working. Once we can teach them English, they absorb learning like a sponge."
Mr Knight has set the TDA a target of filling 17,460 primary training places this year, increasing to 18,640 places in 2010-11. For the first time, this includes employment-based training.