It will not be practically possible for about one in seven schools to comply with plans for compulsory cookery lessons, say head teachers.
Ed Balls wants youngsters to learn cooking skills
The Schools Secretary Ed Balls has promised one cookery lesson per week for one term for 11 to 14-year-olds in England's secondary schools.
But refurbished or newly-built schools might not have the necessary kitchens, says heads' union leader John Dunford.
There is also a shortage of staff qualified to teach cookery, he says.
The government's insistence on compulsory lessons is part of a drive to improve children's diets and to tackle obesity.
But Dr Dunford, general secretary of the Association of School and College Leaders, has cast doubt on the practicality of the plans.
"The government should never have downgraded practical cookery 20 years ago," he said.
"But in the intervening years, schools have been built or refurbished without practical cookery rooms, so it will be impossible for about 15% of schools to put practical cookery on the timetable until they have the proper facilities.
"There is also a shortage of cookery teachers, who will take time to recruit."
Dr Dunford also criticised the idea of adding another compulsory element to the curriculum only months after promising schools greater flexibility.
"They have fallen at the first fence, creating another entitlement and more compulsion for this age group," he said.
But the National Union of Teachers welcomed the proposals, saying that cookery was "an essential life skill and should have been recognised as such in the recent secondary curriculum review".
But the union's general secretary, Steve Sinnott, said that the cookery plans needed to be accompanied by costings for training, updated facilities and extra staff.
The schools secretary's proposals will guarantee cookery lessons from this September for secondary schools which already teach food technology, while those schools which do not teach the subject will have to introduce the lessons by 2011.
A spokesman for the Training and Development Agency for Schools said a recent survey it had carried out showed that almost three quarters of parents (72%) wanted their children to be equipped with everyday life skills, such as planning and making a nutritious meal.
"We are already working hard to increase the number of food technology teachers, and there has never been a better time to go into teaching.
"Eligible postgraduate trainees in secondary food technology will receive tax-free bursary of £9,000 - £225 a week - and golden hello payments of £2,500 are available for eligible newly-qualified teachers who have trained in Design and technology."