Plans to improve school pupils' diets have been cautiously welcomed - but there are warnings that it may not be enough to address childhood obesity.
School dinners will have to be healthier under new rules
School meal menus in England will be healthier - and, from 2008, all pupils will be offered cookery lessons.
But the Association of School and College Leaders said more must be done to change parents' attitudes to food and regulate food advertising.
It also warned that no extra resources had been earmarked for cookery lessons.
Its general-secretary, Dr John Dunford, said: "Schools cannot turn around years of decline in eating habits without major changes in attitude on the part of parents and the food industry, which continues to direct advertising for unhealthy products at children.
"We look to the government to show as much energy and commitment for changing parents' attitudes and regulating food-industry advertising."
'Leaner curriculum needed'
He warned that the curriculum for 11 to 14-year-olds was already overstretched.
"A leaner curriculum is needed to create space for schools to decide what to teach, not for the government to prescribe additional burdens," he said.
"In my view cookery lessons should never have been removed from the school curriculum in the first place, leading to a generation who know how to design a meal or a biscuit, but not how to cook them.
"Bring back cooking, but let schools decide where it comes in the list of priorities."
The NASUWT union welcomed the announcement from the government that £240m extra funding would subsidise healthy ingredients until 2011.
Its general-secretary, Chris Keates, also welcomed funding to build on-site kitchens for those schools which currently have meals delivered.
She also welcomed the introduction of cookery lessons.
But she added: "Careful consideration needs to be given to the practicalities. There must be no expectation that teachers will undertake tuition of cookery skills as extra-curricular activities.
"There will undoubtedly be resource implications, including staffing and facilities. Consideration will also have to be given to whether to charge for ingredients and how this may adversely impact on access for children from disadvantaged backgrounds."
Nutritionists said the cookery classes should be compulsory.
Stephanie Valentine, education director of the British Nutrition Foundation, said: "I would prefer to see cooking lessons in secondary schools made compulsory.
"However, lessons would need to be adequately resourced with equipment, ingredients and facilities, and staff would need to be trained appropriately, to enable children to develop good cookery skills."
Steve Sinnott, general secretary of the National Union of Teachers, added that school catering staff were "the unsung heroes" of education.
He added: "But they need proper training and resources if they are going to counter the attitude of many young people that the best food is the food that is least good for them."