Labour has accused the government of not doing enough to combat a shortfall in primary school places in England predicted for September.
Despite increases in school capacity there will be 120,000 fewer places than there are pupils, according to the party's analysis of government figures.
Thousands of parents "face a summer of worry" according to shadow education secretary, Stephen Twigg.
"When schools start again in September, parents will see more overcrowded classes and temporary classrooms on playgrounds," said Mr Twigg. "In some cases even the school library and music room may have shut to create new classrooms."
Labour's analysis compares the figure of more than 230,000 extra primary places which the National Audit Office has said will be needed by September with the 110,000 places which the government has said will have been created by local authorities.
Scramble for school places
This leaves a shortfall of 120,000 says Labour which will mean many parents "will have to scramble for a place".
A spokeswoman for the Department for Education has countered the claims and said: "The claim that there will be a shortfall of 120,000 places is based on a simplistic and totally flawed calculation that does not take into account existing surplus places.
"In fact, our latest survey shows that there are around 400,000 surplus primary school places across the country and we expect a further 110,000 extra places to be created by September."
"In addition nine out of 10 primary free schools approved last month are in areas of basic need, and last week we announced a further £820m to create 74,000 extra places where they are most needed."
Squeeze on primary places
The squeeze on primary places stems from a rising birth-rate and increased immigration.
In March, the National Audit Office said in excess of 230,000 primary places would be needed in time for the next academic year, with one in five primaries full or near capacity amid signs of "real strain" on places.
The report also warned that although all regions would need more primary places the shortage was not evenly spread. The greatest pressure is in London which accounts for a third of the places needed, it said.