Davis Mukasa, 26, says his time at Christ's Hospital school near Horsham, West Sussex, has transformed his life.
"It raised the glass ceiling for me. Growing up in south London, the expectations were so much lower. To be outside the system was something boys aspired to. If you didn't conform, you were being truer to your black identity."
Davis, who now runs his own events management company, won a free place at the school in 1988. His mother had returned to Uganda and his father was struggling to bring up four boys and hold down a full-time job.
"I was beginning to get a bit unruly, acting the class clown to get attention," Davis says.
"I couldn't be bothered to work and my dad was at his wits' end. But it still upset me when one of my teachers threw my book across the room and told me I'd never amount to anything."
Fortunately, another teacher spotted Davis's potential and suggested that Christ's Hospital might be the answer.
The contrast between Lambeth and the depths of the Sussex countryside proved rather a shock, but Davis says he and the many other inner-city pupils had plenty of support.
"All new pupils have a 'nursemaid', someone from the year above who looks out for you and explains what the school expects from you. Everyone has a tutor they can go to with work difficulties, and we had an understanding matron who helped with any personal problems."
Davis enjoyed the cricket, rugby, camping and the cadet corps - all things he had not had the chance to try before. He also found that being away at school took the pressure off his relationship with his father.
When he left school, Davis found the transition back to city life difficult, but he readjusted by working for two years before taking an economics and politics degree at London university.