The number of children eating free school meals in Hull has doubled in the past year, the local authority says.
Burgers have been banned from many school menus
Hull City Council is celebrating the first anniversary of the project to provide free healthy meals for all of its primary school children.
The aim of the three-year pilot scheme, which costs £3.8m a year, is to tackle underachievement among its school pupils through healthy eating.
Hull is the only English authority to currently provide free school meals.
Councillors have revealed the proportion of children choosing to eat the meals has risen to 75% since May 2004, while in some schools the figure is 95%.
As the popularity of the scheme has increased, the council has boosted the amount it spends on each meal from 37 pence to about 60 pence.
Councillors say 24,000 pieces of fresh fruit and vegetables are now served up across the city every day.
The project is similar to a nationwide healthy eating campaign in Finland, which has been linked to the country's high levels of academic achievement.
Janet Adamson, head teacher at Clifton Primary School, said there had been an improvement in concentration among her pupils since the healthy meals were introduced.
"They always had a certain level of concentration coming back in (after lunch) but that has extended for a longer period now through the afternoon session."
Neil Porter, of the Local Authority Caterers Association, congratulated the council for embracing the initiative.
He said: "I think the council are investing in the long-term health benefits of their children.
"In time evidence to suggest improved behaviour and improved learning will be there," he added.