How do you prevent a child from eating junk food?

One British official reportedly believes the best way to do it is to lock kids inside school grounds to make sure they don't buy unhealthy fast food.

According to U.K.'s Daily Mail, Britain's minister in charge of children's affairs, Kevin Brennan, said grade-school children who attend open campuses should be barred from leaving grounds, after research found kids were leaving to order take out meals filled with fat, salt and sugar.

Only about one third of children eat school-supplied lunches, the paper reported, a number that has been on the decline.

This comes despite a new drive headed by British celebrity chef Jamie Oliver to try and encourage school kitchens to serve more nutritious meals, the Mail reported.

The researchers found kids were opting out of school lunches, not because they were healthy, but because cafeterias had long lines and high prices, the newspaper said.

Click here to read more from the U.K.'s Daily Mail.