John Paul Academy in Glasgow had one of the worst exclusion records in the country.
Pupils were turning up for class in street clothes and trainers and there was a problem with misbehaviour.
But two years ago, head teacher Vincent Docherty took over and clamped down on sloppy dress. Since then, the school has had the lowest exclusion rate in Glasgow and attainment has approved dramatically.
When he started at the 700-pupil school, Mr Docherty introduced a partial uniform of trousers, shoes, shirt and tie, with just sixth year pupils wearing the blazers.
He had planned to phase in the introduction of blazers across the rest of the school, but was stunned when younger pupils asked if they could wear them straight away.
He said: "The huge surprise was parents wanting all the pupils to be wearing blazers and the children asking for them.
"It is astonishing because we would never have predicted that."
Mr Docherty said uniforms played a key part in the school's improvement.
"There has been a dramatic change and the prediction for sixth year attainment this year is the highest the school has had in its history," he said.
The pupils were involved in designing the blazers too, with girls choosing a fitted blazer compared to a suit jacket style for the boys.
I think they all feel grown up wearing them, are proud to be part of the school and are taking their education really seriously.
"We talk about young people misbehaving and the difficulties they get into, but this really is proof of the commitment the pupils are making to the school," added Mr Docherty.
"Wearing uniform has greatly enhanced the youngsters' behaviour and learning."
Stephen Curran, the city council's executive spokesman for education, said: "These are significant improvements and just goes to show what can be achieved when you have the support and backing of the entire school community.
"It is really refreshing that all the youngsters want to wear a blazer and even more so to be proud to wear it. They are exemplar ambassadors for their school and Glasgow."Do you support school uniforms or prefer a more relaxed approach?
Has your child's school changed to uniform and, if so, has there been any change in pupil behaviour?