Tough guidelines on the nutritional value of school meals in England are due to be set out by the government.
Ruth Kelly will pledge to improve school meal standards
Education Secretary Ruth Kelly is expected to say children should get almost one-third of their weekly fibre and protein from their school lunches.
Maximum levels of sugar, fat and salt will be given and it is thought Ms Kelly will say school meals should have two portions of fruit and vegetables.
Junk food will be banned from schools from next September.
The nutritional standards will be given to schools from this autumn, and will be made mandatory by autumn 2006.
Nutritional standards were introduced a few years ago for meals in Scotland's schools.
In an announcement last week, Ms Kelly said the "scandal of junk food served in school canteens" had to end.
Certain foods, including poor quality meat, would be banned from school meals, she said in a speech to the Labour Party conference.
And school vending machines would not be permitted to stock chocolate, crisps or fizzy drinks from next September, the secretary of state said.
The School Meals Review Panel, an expert advisory group on school meal standards, is set to announce detailed nutritional standards for school meals on Monday.
The panel was set up by the government in response to a campaign by TV chef Jamie Oliver to improve the quality of school meals.
And the government said the amount of money spent on each school meal would rise to 50p in primary schools and 60p in secondary schools from this term, to become mandatory next September.
According to guidelines released earlier this year by the Caroline Walker Trust, which has been advising the government on school meal standards, meals should give children 40% of the recommended levels of zinc, iron, calcium and vitamins A - C over a week.
The trust says the number of school-age children who are obese has doubled since 1992.
More nutritious school meals could help stave off diseases such as coronary heart disease, diabetes and cancer in later life, it says.
The trust also says packed lunches should contain at least two portions of fruit and vegetables.