Jamie Oliver's healthy school dinners have produced a marked improvement in national curriculum test results, research has found.

A study by the Royal Economic Society shows children reared on the healthier dinners that the TV chef introduced into schools did far better in tests for 11-year-olds.

Researchers Michele Belot, from Oxford University, and Jonathan Jones, from Essex, looked at the test results for pupils in Greenwich schools who started their school life in 2004 - the year that Oliver's Channel 4 series launched its healthier school dinners campaign in 80 of the authority's schools.

They said there was a three to six percentage point improvement in the number of pupils reaching the required standard in English tests in the schools surveyed, which were serving healthier lunches, and a three to eight percentage point improvement in the numbers attaining a higher level science pass - thus having the ability of the average 13-year-old.

Nationally, the percentage reaching the required standard has remained almost static over the past six years.

In addition, the number of children marked down as having authorised absences - mainly off sick - showed a 15 per cent decrease.

"It is possible that the programme will continue to have an effect on children's behaviour and health through adolescence," the researchers concluded.

They added that - even if the benefits are only short-term - they have had just as much effect in raising standards as the introduction of the literacy hour in the late 1990s.

Oliver's campaign saw low-budget processed meals high in saturated fat, salt and sugar replaced by a healthier option. Turkey Twizzlers were banned and replaced with a nutrient-rich diet with more concentration on coconut, fish and broccoli.

Oliver said: "The research results are fantastic. This is the first time a proper study has been done into the positive effects of the 'Feed Me Better' campaign and it strongly suggests we were right after all.

"Even while doing the programme, we could see the benefits to children's health and teachers - we could see that asthmatic kids weren't having to use the school inhalers, for instance. We could see it made them calmer and therefore more able to learn."

The results coincide with a survey by the UK's Association of Teachers and Lecturers which shows two-thirds of primary school staff and 53 per cent of secondary school staff believe every pupil should have access to a free school meal.

Tom Huck, a primary school teacher from Boston, Lincolnshire, said: "A healthy hot meal each day would mean some control over their diet, improve table manners, improve tolerance of each other and hopefully mean better behaviour in the classroom in the afternoon."