Paul Watson, by his own admission, was "a terror" in S1 and S2.
But after taking part in the Prince's Trust's "xlerate with xl" programme at St Paul's High, his behaviour was turned around.
Last year he was the programme's "young person of the year" and was chosen to meet the US president, George Bush, and the Italian Prime Minister, Silvio Berlusconi, when they arrived at Prestwick airport for the G8 summit.
"It's not every day that people can say they have met George Bush," Paul says proudly.
Now in S4 in a non-accelerated class, he plans to stay on to S5 and would like to become a model, presenter or actor.
Michelle McQueer, also in S4, was encouraged to take part in Xl because of her painful shyness. She recently made a confident public presentation and hopes to join the fire brigade.
"The teachers are brilliant. They really get on with you and treat you like friends as well," she says.
Three of the pupils now in S5 who were in the first fully-streamed S1 class attribute the school's success to its happy atmosphere and the teachers'
high expectations and good relationships with them.
Samantha Boyle was in one of the two accelerated classes. She left at the end of S4 and had planned to do her Highers in college. But, surprised at her good passes, she is now back in St Paul's because, she says: "I am used to everyone here and I like the environment."
She got a B in Higher music, an Intermediate 2 A pass in business management, and six Standard grades (four Credit passes at level 1 and two at level 2). This year she is doing five Highers.
Marc Wood was also in the accelerated class. He says: "The teachers are generally really nice to you. I tell them things I won't tell anyone else.
I trust them."
He got a B in Higher music and eight Standard grades (three Credit passes at level 1 and five at level two). He wants to go to Glasgow University, possibly to study law.
Maria McAulay was not sure if she had been in the accelerated class or not - and Marc and Samantha didn't know if she was. Checks with the headteacher confirmed she was in one of the other classes - the pupils' confusion appears to confirm the lack of hierarchy.
Maria got two Intermediate 1 passes at A and C, and eight Standard grades (four Credit passes at level 2 and four General passes at level 3). She wants to be a nursery teacher.
Marc says: "Because you are put in a class by ability, everyone around you has the same ability and you don't feel different. Everyone's kind of equal."
Maria adds: "It's up to you - it's your education."