The Mayor of London, Sadiq Khan, has announced that all primary school children in the city will get free school dinners for a year from September, with his £130m plan set to offer all children, regardless of the amount of money their parents earn, a free lunch at school.

One charity, the Children's Food Campaign, said it's "utterly delicious news!", saying it will help London children "concentrate, play and learn."

But some politicians say the money should be spent on free school dinners for secondary school pupils from struggling families.

Over the years there has been a lot of research into pupils eating regular meals and the effect on the way they learn. Researchers say that eating properly helps children learn more effectively. A government trial which gave every primary school student free lunch for two years in 2009-2011 showed students did better at school because of it.

Celebrity chef Jamie Oliver, who is campaigning for free school meals for children in families struggling with money, said: "We know in every way, shape and form that kids who have a decent lunch and breakfast learn better, their educational attainment is better" He joins football star Marcus Rashford who campaigned for free meals for children in families who are in poverty and struggling to pay for basic things - like food, housing and energy bills.

There's lots of research which says making sure we all have a proper lunch is important - but who should pay for it? Lots of charities & food campaigners say giving everyone free school dinners benefits everyone because children are happier, healthier and do better at school - meaning they go on to get better jobs and contribute more to the UK.

Many say the government should pay for them with taxes - the money adults pay to the government to fund things like hospitals, healthcare and policing. The Mayor of London says giving everyone a free lunch will stop anyone feeling "shame or embarrassment" for getting them.

The Labour politician says he's "repeatedly" asked the UK government to give free schools to more children, adding that the difference they make can be "truly game-changing." But some of his opposition say it's not fair some London primary school children from wealthy families get free meals when high school children may have to pay for them even if their families struggle - because the free school meals only apply to primary school pupils.

"If the mayor genuinely wants to help the poorest families, he should be focusing on those most in need across all schools," says Emma Best, a Conservative politician in London.

Charities and unions have welcomed the news but say more action is needed.