The undergraduate ambassadors scheme involves a one-day crash course in teaching for maths and science undergraduates, a period of classroom observation, and finally a project devised by the students for pupils.
This year nine universities are taking part, and 95 undergraduates have been placed in around 40 schools.
Placements earn students credits towards their degrees. More than 30 universities have said they are interested in joining the scheme this September.
Dr Anne Skeldon, a lecturer in Surrey university's maths department, where four undergraduates signed up to the scheme last year and 16 this year, said: "I thought it would be great if undergraduates got involved in teaching in a low risk manner. This way they don't have to invest a year of their time in a postgraduate certificate in education only to find out they don't like it."
Maths student Helene Heslop, 23, graduates from Surrey university this summer. She has been at St Peter's Roman Catholic school, near Guildford since January 12.
Ms Heslop, who is now considering a teaching career, said: "It's been interesting to see how much more reluctant the girls are to answer questions than the boys. The boys will just have a go."
Ravi Kapur, the national director of the scheme, said: "It's been good news stories all round. The undergraduates went into schools across the range, from grammar schools to tough inner-city schools. One school burnt down twice during the placement, but the undergraduate still had a great time."
Simon Singh (see comment above), the author and broadcaster whose idea the scheme is, said: "We've had an astonishing take-up. At Southampton, for instance, 13 maths undergraduates signed up, and out of those 10 went on to teacher training. One was offered a contract until the end of the year, which highlights the desperate need for teachers. He went on to do a PGCE."