Schools must do all they can to tackle the way unhealthy foods are marketed to children, the Food Standards Agency said this week.
The agency said school vending machines should sell healthier snacks and that a lot more must be done to encourage children to make more informed choices at mealtimes.
Sir John Krebs, chairman of the FSA, said: "Too many foods aimed at children are too high in fat, salt and sugar.
"Parents want to give their children healthier diets and it is not always clear what the healthy choice is at the supermarket, restaurant or school."
The independent agency will consult with local education authorities and schools on ways to achieve the recommendations, and guidelines on best practice will be published.
New guidelines on the use of vending machines will be in place by December, and proposals for improving school meals will be published by the autumn.
The FSA said it will also publish nutritional criteria for the food industry in a bid to reduce the levels of fat, sugar and salt in foods aimed at children.
The guidelines will not be legally binding, but the agency will monitor the food industry to see what action it is taking. Supermarkets will be urged to signpost healthy food for children.