For the one in 10 schools without proper kitchen facilities, providing high-quality hot meals is a problem even before new government standards come into effect.
A possible solution is a method which allows the schools to use microwave power to steam-cook raw food, rather than heat up pre-prepared meals.
The TES went along to Sacred Heart primary school in Islington, north London, which introduced microwaved meals four months ago, to see how they went down with pupils.
A typical day's lunch menu consisted of pasta carbonara or vegetable korma with peas and coleslaw, followed by a chocolate muffin or fresh fruit.
Philip Ward, nine, said: "They're great. Before, the meals were nice but they weren't very healthy. Sometimes we had hot dogs or burgers. Now they are healthy and taste better. I like the potatoes in gravy best."
Anna Lasok, also nine, said: "I like the different types of pasta and puddings. They definitely taste better."
John Lane, headteacher, said: "The meals are very good. We don't have a proper kitchen, so previously pre-prepared food was left on a hotplate.
"It could stand around for long periods so the children had food which had lost a lot of its nutritional goodness."
The number of pupils eating hot meals has increased from 130 to more than 250 since the school introduced steamed meals.
The school is one of about 20 to adopt the Esteam dinners, produced by Scholarest, this year.
Steve Kemp, a spokesman for the company, a division of Compass Catering, said that the meals meet new government nutritional standards set for September.