Banning you from leaving school during your lunch breaks would help to stop you filling up on junk food, teachers are being told.
A group set up by the government to try to improve pupils' diets in England reckons a lunchtime lock-in would see pupils choosing healthier school meals.
The School Food Trust says there are too many takeaways and sweet shops near schools, encouraging kids to eat junk.
But head teachers have warned the ban would be very difficult to carry out.
In some parts of England, pupils have a choice of more than 40 fast food shops and takeaways near their schools.
The Trust said a ban on pupils leaving their school grounds was one way of tackling the temptation they offer.
Some schools already stop children leaving at lunchtime and it seems loads of parents agree with the idea.
Nine out of 10 of all the parents asked by the Trust said they thought their kids would eat more healthily if they weren't allowed out of school.