The proposals include target maximum values for total fat, saturated fat, total sugar and salt for manufactured products used in school meals, as well as minimum values for protein for vegetarian products.
The specifications would be voluntary but manufacturers supplying foods to school caterers and caterers supplying school meals would be encouraged to adopt these specifications, said the Food Standards Agency.
The proposals are part of a far-ranging government plan to improve children's nutrition, and follows heavy attack of school food by celebrity chef Jamie Oliver.