School caterers should ensure every menu choice meets nutritional standards because children will nearly always opt for chicken nuggets and chips rather than a salad.
The call for overall healthier meals comes from the Consumers' Association, whose recent Which? report found that the current standard of school meals had failed to improve the diets of schoolchildren.
The report found that while school caterers were meeting the standards set by the Government in 2001, school meals were contributing less than one portion of fruit and vegetables a day to children's diets because they opted for less healthy options.
But contract caterers dismiss the idea, claiming it would lead to higher levels of waste and hungry children.
A spokeswoman for Initial Catering Services, which has contracts at 2,500 state schools, said: "Many children will only eat familiar food and will not try alien foods, such as home-made dishes or vegetables.
"If children are more used to eating convenience or fast food outside school hours, then that is what they will look for at school.
"If it's not available, they may choose not to eat anything, leave large amounts of wasted food, or choose to bring a packed lunch and fill up on snacks such as crisps and chocolate biscuits."
Sue Kilbey, chairman of the Local Authority Caterers Association (LACA), agreed: "Forcing food on children that they do not recognise, let alone eat at home, is not the way forward."
She said encouraging children to choose healthy food was a task that caterers, parents, producers, high-street outlets, and the education system itself had to collectively tackle.
The Scottish Government has recently announced an extra £63.5m over three years to implement its nutritional standards programme. England and Wales received no extra funding for its standards in 2001.
Results of the Government's own survey of school meals are expected in 2004. The Department for Education and Skills said any policy review would not be made until then.
By Ben Walker