Come September, children at Mudeford infants school in Dorset are not going to be getting hot school dinners. They’ll be eating sandwiches. Somewhere along the troubled history of the coalition’s policy to give all infant children a free school meal, the requirement for food to be hot quietly disappeared, to the relief of some headteachers.

“With declining budgets we just don’t have the finances to employ the staff to serve hot meals,” Mudeford’s head, Duncan Churchill, explains. “We’ll get the money for the actual food, but no extra money to run it. And I’m not going to make teaching assistants redundant in order to employ serving staff.”

Some school leaders argue that the proposed sum of £2.30 a child being paid by the government will buy a hot meal – but not what is needed to supply it. Churchill’s choice highlights a dilemma. If it’s not enough, where do schools get the money to fund this new legal requirement for free meals?

Ministers have recently woken up to the fact that heads are saying they’ll have to spend teaching and learning money to cook and serve meals, supervise lunches in newly equipped dining halls, clear up and dispose of the waste.

Churchill runs through the figures. “For the food element we’ll get £50k. It would have cost us another £10k a year to staff hot dinners. With sandwiches, there are still significant costs: I’ve been quoted £10k for an external cold room to keep the dinners fresh when they come in. The local authority gave me a capital grant of just over £4k. So I now have to find £6k to buy this fridge.”

That money will have to come from Churchill’s capital budget (money he’d planned to use for ICT equipment) and from his school development budget – that’s staffing, textbooks and anything else children need in class. He’s not happy about it. “£56k is being spent to give children a sandwich,” he says. “Give me £56k to spend in other ways and I could transform the educational chances of children at this school.”

Schools could be made to buy local produce and in season British fruit and vegetables under plans being considered by ministers.

George Eustice, the farming minister, said that the Department for Education is working on measures to ensure that schools across the country use British produce in their meals.

Mr Eustice told MPs on the environment, food and rural affairs committee that from September, schools will be told by the Government that they should be buying local produce.

He said that Michael Gove’s education department is working on a “school food plan” that will “encourage” the use of fresh, British products in children’s meals.

Britain imports billions of pounds of food every year – nearly a quarter of all food consumed every year – and ministers are keen to encourage more local suppliers.