School dinners in England will be free from chocolate, crisps, fizzy drinks and "low-quality" meat from the autumn, the government has announced.
School meals have been criticised for their poor nutritional content
Education Secretary Alan Johnson has published nutrition guidelines banning meals high in salt and fat.
These would "undo decades of neglect" and improve pupils' health, he said.
The standards, based on recommendations by the School Meal Review Panel, follow a campaign by TV chef Jamie Oliver to improve the quality of school dinners.
Fruit and vegetables
From September, caterers will ensure "high-quality meat, poultry or oily fish is available on a regular basis", the Department for Education and Skills said.
Pupils will get "a minimum" of two portions of fruit and vegetables with every meal, while deep-fried food will be restricted to two portions per week.
Mr Johnson said: "These new standards will start to undo decades of neglect and ensure that healthy eating is the norm in every school.
"The health of our young people is not an area for compromise.
"Providing pupils with a healthy balanced meal that will give them the energy, vitamins and minerals they need to learn and play is essential, but we will go further, helping schools to teach every pupil skills in diet, nutrition, practical food preparation and cooking to ensure they make the right choices throughout life."
Last year the government promised £280m to improve school meals, following Mr Oliver's campaign.
This is aimed at ensuring a minimum of 50p per head for school meal ingredients of in primary schools and 60p for secondaries.
From 2008, primary schools will be told to impose "more stringent nutrient-based standards" - stipulating vitamin and mineral content.
FOODS TO BE BANNED
Burgers and sausages from 'meat slurry' and 'mechanically recovered meat'
Sweets including chewing gum, liquorice, mints, fruit pastilles, toffees and marsh mallows
Chocolates and chocolate biscuits
Snacks such as crisps, tortilla chips, salted nuts, onion rings and rice crackers
Secondary schools will follow a year later.
Kevin McKay, the chairman of the Local Authority Caterers Association, told Five Live what the guidelines would mean in practice.
"Certain things like fried products will be down to twice a week and certain other elements are being banned from vending machines; confectionery, snack sales, those areas," he said.
"And then what we're expecting is to have some nutrient-based standards; a meal will have to meet certain regulations as far as the nutrients, so we're talking levels of iron, calcium and fat levels."
A Soil Association report suggests spending on ingredients by primary schools has increased from an average of 47p per pupil per day in 2005 to 51p this year.
LIKELY TO BE EXEMPT
Bread products such as crumpets, English muffins, bagels and croissants
Cakes and biscuits made fresh by school caterers, digestive and ginger nut biscuits, cake bars, iced buns and doughnuts
Dried fruit, unsalted nuts, peanut and raisin mixes and unsalted popcorn
But some are still spending as little as 41p per child per meal, according to its survey of 74 local authorities in England.
The number of obese or overweight children in Britain aged between two and 15 has risen to about 30% in recent years.
Meanwhile, poor diet accounts for around a third of deaths from cancer and heart disease.
The consumer group Which welcomed the new guidelines, but warned that children were still vulnerable to marketing tactics from the food companies.
"Unless there are tighter restrictions on the way companies market unhealthy food to children, it will be hard for parents to reinforce the healthy eating messages out of school," said Which chief policy adviser Sue Davies.
Mick Brookes, leader of the National Association of Head Teachers, has blamed schools' "gastronomic Puritanism" for encouraging children to eat at nearby chip shops instead.
The teachers' union the NASUWT said the recommendations would make a "valuable contribution to improving the health and wellbeing of youngsters".
But it too expressed concern about the "increased bureaucratic burdens".
Plans elsewhere in the UK
The School Meals Review Panel first outlined its recommendations last autumn, following Mr Oliver's campaign.
The Scottish Executive is also planning to ban junk food from schools and to create a law encouraging more pupils to eat school meals.
In Wales, a working group on nutritional standards is due to publish a report next month.
A Welsh assembly government spokeswoman said it would use its powers "to take junk food out of our schools".
Northern Ireland's education department has put out proposals for public consultation.