Schools could vary the size of their buildings and teaching staff every year to fit in with parental demand, under plans being considered by Labour.
Proposals aimed at increasing parental choice have been put forward by Stephen Byers, the former education minister who is advising the Prime Minister on Labour's manifesto.
The date when parents pick secondary schools would be bought forward by almost a year.
Labour members are expected to discuss the plans at the party's spring conference in Newcastle this weekend.
A parent whose child starts school in September 2007 would pick their secondary in January 2006, instead of the following autumn, allowing decisions to be finalised by July that same year.
Mr Byers also proposes that funding should follow each pupil and that popular schools receive "new" freedoms to expand. Writing in Progress, a policy magazine for Labour modernisers, he said that the existing admissions system was "just about rationing out places at good, popular schools". "With the longer lead-in time, schools will be able to plan ahead and take on the necessary extra staff and provide any additional accommodation that might be needed," he said.
Mr Byers said the plans would make the transfer from primary to secondary less disruptive.
But Steve Sinnott, general secretary of the National Union of Teachers, said: "Schools just can't expand in the time suggested. There would also be serious instability of staffing."
John Dunford, general secretary of the Secondary Heads Association, said the plan would lead to "mobile classrooms spreading across the land".
"You can tell there's an election coming when Stephen Byers floats a Downing Street idea," he said.