Matthew Goodgame, drama co-ordinator, beat more than 2,000 chorus-line hopefuls in Musicality, Channel 4's search-for-a-star series, to land the lead role in a one-off performance of Chicago, at London's Adelphi theatre.
For the past month, he has been rehearsing under the guidance of West End luminaries. "My dreams have come true," he said. "I have to pinch myself."
Mr Goodgame is on sabbatical from St Saviour's. But, when he returns to Westgate-on-Sea next term, he plans to pass on his new knowledge to the drama group.
"I used to draw on what I knew from amateur dramatics," he said. "But now I'll know what to say to get the best performances, because it's been said to me.
"I'll know how to bring out the comedy, or to look at the detail. Though, obviously, it's a bit different with seven to 11-year-olds."
Mr Goodgame has been sending messages to his class, and in return they have sent portraits of him: "They drew me with muscles, which I was quite pleased with."
But he said any images they have of his celebrity lifestyle are unlikely to be reflected in reality: "I'm not planning to go to any premi res, or date any celebrities.
"It would be nice if some of the pupils want my autograph. Once you're autograph-signing, you know you've made it."