Hull's Thomas Ferens Academy says it "deeply regrets" refusing to hand GCSE results out to pupils in a dispute over tablet computers.
The school was accused of blackmailing pupils, telling them they could not have results until they paid the balance on their iPads.
About 20 youngsters who were affected were forced to look on yesterday as their friends were handed envelopes to open.
Today, chair of governors at the academy, Richard Heseltine, issued an apology.
He said: "We deeply regret the apparent breakdown in communication.
"Clearly, students should be informed of their results."
Pupils were eventually given their grades at 12.30pm after a group of parents gathered at the school to demand them.
Children at the school, in one of Hull's most deprived areas, take part in a scheme that sees pupils given iPad tablets.
Under the agreement, parents would pay £12 per month for the equipment, which would eventually be owned by the pupils.
However, some parents fell behind with repayments because of financial hardship.
Parents are angry they were only told at 5pm the night before their children would be refused their results.
Leah Sawyers, 16, said: "I waited a really long time to find out my results and I think it's disgusting that they wouldn't let me find out what I got just because my mum can't afford to pay the money.
"It's just pure blackmail.
"To watch all my friends open their results and for me to still not know what I got was heartbreaking. Some people don't have the money to pay back the full balance.
"It's ridiculous – we were only told about this the day before.
"My mum was really, really upset."
Leah's mum, Angela Fox, said the school should not have taken it out on the children.
She said: "It was not their fault. The kids had psyched themselves up for this for the last couple of weeks. Yes, I do agree as parents it's our fault, so why take it out on the kids?
"I'm furious. All the work they have done and the pain and the worry about results and this happens. To turn up at the school and be refused their results is disgusting."
Ms Fox said she had paid off about £120 off the balance of the iPad. She said if she handed the iPad back, she would lose the £120.
"We have struggled to pay it," she said.
"I went in to try to find a way I could pay for it. I'm happy to go in and do so but it was refused. "What they did was out of order."
Councillor Rosie Nicola, portfolio holder with responsibility for education, said it should not have happened.
She said: "You can't visit on children the difficulties their parents are experiencing.
"I am really unhappy that there are practices like this and it is not something that should have happened. I am glad the chair of governors has said what he said.
"It is not acceptable. Children turn up because they want to know their results and we have all been there, it is horrible, you are terribly nervous and then to be told you are not having them because of something you can't control is very unfair."
The package, which is subsidised by the school, is worth £500.
Last year, parents reacted with anger when pupils had their iPads taken away two weeks before they sat their crucial GCSE exams, in another dispute over payments.
• Provisional results for Thomas Ferens Academy show that just 20 per cent of pupils gained the GCSE gold standard.
The school had been warned by the Government it must improve its results.
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