Schools will soon have "no excuse" for serving poor quality meals under a £280m overhaul of catering, Education Secretary Ruth Kelly says.
Ruth Kelly promised to end a 'vicious cycle'
Training for cooks and higher nutrition standards will end "cheap slop", dinner staff at a conference in London heard.
Some 15,000 kitchen workers in England are to begin courses from September, covering how to prepare fresh food.
The public sector union Unison says staff need to be given more time to create "decent meals from scratch".
It also wants the government to take on more cooks.
'Junk food bans'
Ministers are giving £220m to schools and local education authorities for ingredients so at least 50p is spent on dinners for primary school pupils and 60p for secondary school children.
The School Food Trust, which is receiving £60m, is looking at banning certain junk foods and studying how schools can get out of catering contracts.
The changes follow a campaign by TV chef Jamie Oliver to improve nutritional standards in schools, amid rising rates of childhood obesity.
Ms Kelly told the conference, organised by Unison: "No one wants to serve up cheap slop. But we cannot send Jamie Oliver to every school."
She added: "We have to reverse the trend where a majority eat too much fat, sugar and salt and only a minority eat five portions of fruit and vegetables a day."
Ms Kelly also said: "If there is a vicious cycle, we can break it."
However, Mr Oliver predicted the situation would be "touch-and-go for the next year or so because the crisis in school meals is so huge that it will take massive change to improve things".
Shadow Education Secretary David Cameron said a "clear strategy", including a junk food ban, was needed.
Christian McAnea, Unison's head of education services, said: "The staff have been doing their best with the resources and time available but we want them to be given the time to cook meals from scratch.
"This can only be done by increasing the hours they work and employing more people."