A school has been criticised after sending 70 students home for failing to meet a strict new uniform code – without notifying their parents.

City of London Academy Islington (COLA-I) in Prebend Street dismissed the pupils on Wednesday morning of last week – the first day of the new term – and sent them home with letters detailing the breaches.

Angry parents claim the school broke a duty of care but the academy insists the stringent discipline is vital in driving up standards.

A number of students were dismissed for not having the required rucksacks emblazoned with the COLA-I emblem, but the academy later relaxed the criteria after finding out the uniform stockists had sold out of the bags.

Parent Patrick Coogan, of Clerkenwell Close, Finsbury, whose 13-year-old daughter Georgina was sent home, said: “They acted like lunatics, sending children onto the streets.

“I believe the school has a duty of care to all the children between the hours of 8.45am and 3.15pm unless they contact the parents – which they did not do.”

Mr Coogan said Georgina remained off school yesterday as the required skirt had still not arrived at the uniform stockists.

Another parent, who did not want to be named, said her 13-year-old daughter was sent home for having a plain black bag without the COLA-I emblem.

She said: “I want a written apology. I don’t even let her go to the sweet shop on her own, but she had to travel all the way home.”

Both parents said they had not received any letter detailing the changes.

But COLA-I’s executive principal Mark Emmerson, who took over the school in April, having turned around another struggling academy in Hackney, said the uniform change was the subject of a letter posted to all homes in July as well as a text message to parents on Tuesday of last week – the day before term began.

He said: “We are not obliged to allow the children into school without the correct uniform.

“The vast majority of the children were stopped at the gate, sent home and were back within half an hour. I was prepared to sacrifice the first day of teaching as this is part of our strategy to increase and improve standards.

“I want the school to do well and I think the school has turned around dramatically already.

“But when rules are laid down, students and families have to meet them.

“It is difficult for some children because they had been used to flouting the rules without any consequence – but this is not the case any more and the majority understands that.” He urged people to visit the school at next Thursday’s open evening to see the positive impact of the tougher approach.

While a spokesman for the Islington branch of the National Union of Teachers agreed uniform rules needed to be adhered to, he said: “I think that young students should not be sent home without parents being informed unless absolutely necessary.

“Occasionally, if something happens such as the heating breaking down then they can’t reasonably keep the children there, but in circumstances where it’s avoidable they shouldn’t be sent home, especially when the breach of regulations are not the fault of the children or their parents. The school should have adopted a more flexible approach.”