And a separate study out this week also highlighted serious concerns over the quality of food being offered in primary schools.
Secondary schools were condemned for failing to meet national nutritional standards set out in 2001, in a joint survey between the Department for Education and Skills and the Food Standards Agency.
It found healthy practices - such as restricted access to table salt, use of low-fat spreads in sandwiches and providing oven chips instead of fried chips - were adopted in only a minority of schools.
The survey also identified a lack of guidance in healthy catering given to canteen staff, with only a quarter having undergone training in the past year.
Cakes and muffins were served more frequently at most schools than sandwiches and fruit, and more than a quarter did not even serve fruit juice.
The quality of food also varied dramatically between the start of lunchtime and the end. For example, 83 per cent of canteens met nutritional standards at the start of the service, but this had dropped to just 47 per cent for those at the back of the queue. High-fat main meals such as burgers and chicken nuggets were served on at least four days a week at 86 per cent of schools and chips cooked in oil at 76 per cent.
The study of 79 secondary schools in England concluded: "While schools offered a wide variety of foods, the overall balance of foods on offer was not healthy."
The report, School meals in secondary schools in England, called for greater manipulation of menus to promote healthy choices and more encouragement of schemes such as smartcards to reward those choosing healthy options.
The second study, also by the Food Standards Agency together with the Office for Standards in Education, found that effective food policies were being promoted at only a handful of primaries.
David Bell, chief inspector, said: "Food fads and foibles are developed at an early age so it is important that we help encourage and educate children about healthy eating habits at the earliest stage possible."
Nurseries were found to be better at promoting healthy eating than primary schools.
The report recommends the Food Standards Agency website as a starting point for teachers, parents and children wanting accurate and unbiased information about nutrition and diet.
Shaw Cross nursery and infants in Dewsbury, West Yorkshire, was one school highlighted for its good practice. It has introduced a Friday "cook day", when parents are encouraged to come into school and cook with their children. Carol Page, headteacher, said: "This week they have been trying fruit smoothies with bananas and strawberries."
The Government admitted many school canteens failed to live up to the levels of nutrition promoted to secondary-school pupils during lessons. It has published a Healthy Living blueprint of what teachers can do to encourage pupils to adopt healthier lifestyles.
* A website with a database of more than 10,000 sporting facilities, from pools to ski slopes, has been launched, backed by pound;5million of lottery money, with more expected to be added.
HEADS' FITNESS, LEADERSHIP 23