A council wants to expand a secondary school before it has even opened - because it is not big enough.
Parents have battled since the Sixties for a new school in Peacehaven.
But there was an outcry when 179 parents applied to send their children to the school for the first take in September, and only 150 places were offered.
It meant East Sussex County Council would have turned down parents living in parts of Peacehaven, Telscombe Cliffs and Saltdean.
Yesterday, the council agreed to increase admissions to 172, allowing children from the allocated local area into the school.
But now the council has realised the total admissions figure of 750, set after consultation with the Department of Education, is not high enough to cope with expected demand.
It is now bidding for millions of pounds to build more classrooms to accommodate about 900 pupils.
This is expected to cost another £4 million, which the council will pay back to the private company building and maintaining the school.
The council assumed many local children would want to follow their siblings to schools in Brighton, Newhaven and Lewes but this has not turned out to be the case.
Estate agents are also attracting potential buyers into the area by publicising the prestigious new school.
Councillor John Livings, who represents Peacehaven, said: "To exclude any of the children whose parents and grandparents fought for 30 years to get a secondary school in Peacehaven would have been unacceptable.
"Happily this has not happened and the school can look forward to being part of a true community with the school at its heart."
He added: "The school has credit to admit 150 pupils a year. This year it can cope with admitting 172 because there will be plenty of space but when it becomes full there will not be enough classrooms."
Baldez Soni, chairman of the governors at the school, said: "From the governors' point of view, we felt demand would be more than 150 a year.
"I think they made some false assumptions that some of the children would follow their siblings or go into private education rather than go to their local school."
Peter Weston, assistant director of pupil and family services at the council, said there had been a long battle to get a Private Finance Initiative for the school to be built.
He said: "We had long hard negotiations to get a school at all because according to Government criteria it was not necessary."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article