Riddlesdown High School is a popular establishment. More than 700 children applied for places at the grant-maintained school this year.
Not every applicant could get a place at this thriving south London school - but more than 300 children did.
The London borough of Croydon thought it was too many, and a clear example of why Government plans to expect opted-out and local authority schools to work together to regulate admissions are doomed to failure.
Croydon education officials say that last September they had expected 240 new pupils to join Riddlesdown high the following year. In January that figure increased to 270 - but at the beginning of this term they discovered the actual number was 306. Other schools were undersubscribed.
Dr David Dibbs, Riddlesdown headteacher, says he gave regular updates on pupil numbers, and does not make any apologies. He says it is impossible to know the exact numbers who will take up offers because many parents apply to several schools.
"To protect ourselves from that we have to over-offer," he explains. "This year not as many pulled out as we've been used to - and we've ended up with rather more than I would have liked."
Before the school went grant-maintained in 1991, there were just 922 pupils: now numbers have risen to 1,300 - plus another 120 in the sixth form.
He says: "It's better to be expanding than dwindling. And you might think the council would be grateful on the odd occasions when a school does help parents get their wish by going a bit over its number."
Just a few miles along the road at Haling Manor High, headteacher David Troake had expected 130 pupils to join the school in September - only 83 did.
Mr Troake says: "I've got a Pounds 150,000 problem because Dr Dibbs has increased his intake. In a place like Croydon you've got more than a dozen different admissions systems, with GM, two city technology colleges and the LEA. It's a mess and it allows for maverick behaviour.
"Parents are astute enough to play the system and keep several places open, and it leads to chaos: the only way to improve it is to create an independent admissions authority."