Mr Winn, a maths teacher and rugby coach at Blackwood comprehensive in Gwent, faced a steep learning curve.
"I didn't know anything about business, but he said just have a go and see what happens," Mr Winn said. "It was on a voluntary basis but would look good on my CV - that's what he said."
The head was right. Mr Winn's work won him this summer's teaching award for enterprise in Wales 2006, with judges praising his verve, gusto and the impact his dedication has on students.
Last year his team won Young Enterprise company of the year in Wales, and the team's managing director, Zowie Purves, then 15, was honoured as young achiever Welsh woman of the year.
Head Mike Pickard said: "Andrew's award properly recognises what some people think is an old-fashioned idea - teachers who put time into subjects outside their own area to provide children with additional opportunities."
Mr Winn, 35, grew up in Griffithstown, near Pontypool. After a degree in maths he took his postgraduate certificate in education at the University of Wales Institute, Cardiff, and completed a masters in education in 2003.
Young Enterprise is a charity which aims to encourage entrepreneurs of the future. In Blackwood, Year 10 pupils run a real company for a whole year and make money which is theirs to keep if they want to.
They come up with an original business idea and appoint directors of finance, marketing, personnel, sales, operation, ICT, and a managing director to see it through.
Mr Winn helps the team at lunchtime and after school - one day they did not leave until 7.45pm - offering advice and motivation. "Pupils can resign or be sacked, it's tough," he said.
Last year's winning team produced a bilingual CD-Rom of bedtime stories, read by Welsh actors, including Matthew Rhys, Brian Hibbard and Boyd Clack.
It was endorsed by the Children's Hospital for Wales, and the students donated pound;1,000 to them at the end of the year.
"I'm quite a competitive person," says Mr Winn, but adds there was also great satisfaction in seeing the pupils grow.
"I think they pick up skills and realise qualities they have in a way that wouldn't happen in the normal classroom environment.
He adds: "I just love what I'm doing. Teaching is my chosen career - I wouldn't want to do anything else."