Doctors and head teachers are calling on the government in England to look at providing free breakfasts to children on free school meals.
They say such a move would help tackle health problems linked with poverty and boost academic achievement.
The call comes from the Royal College of GPs, the National Association of Head Teachers and the Royal College of Paediatrics and Child Health.
A Guardian survey said half of teachers questioned gave food to pupils.
The newspaper's research involved 591 teachers in the UK.
Of those, half said they had taken food in to school to give to pupils who had not had breakfast. One in six said they had given pupils money to buy lunch.
Steve Iredale, a head teacher from Barnsley, said he had taught at six schools and had been aware of this going on in all of them.
"We have all done it, in all types of school. You find a way: keep biscuits in the office, bread in the office. Occasionally you see a distressed child who is hungry."
Mr Iredale, who is also the president of the National Association of Head Teachers, said he would like to see a trial in schools where free breakfasts were provided either for all children who wanted one or for those entitled to free school meals.
The three associations are calling on ministers to look at the feasibility of providing free breakfasts for pupils from poor families.
The Royal College of GPs says ensuring children have breakfast could help combat diseases related to poor diet in childhood such as anaemia and stunted growth.
Dr Clare Gerada, from the organisation, said: "I'm quite upset that children are going to school hungry. How are children going to learn if they are hungry?
"Some people are being negative, saying 'Why aren't the parents providing this?'. There is parental responsibility but there is also some real poverty out there."
Children 'not a priority'
Many primary schools run breakfast clubs where children can go from 0800 or even 0700, but usually for a fee, while many secondary schools open their canteens in the morning so children can buy food.
Through the charity the Mayor's Fund for London, free breakfasts are going to be provided at 50 schools in some of the capital's poorest areas.
The charity Magic Breakfast runs pre-school clubs in schools where at least half of pupils qualify for free school meals.
It says demand has been growing.
A spokesman for the Department for Education said: "We know how important it is for children to have a healthy breakfast.
"Many schools provide breakfast clubs as part of their extended services, which can improve children's attendance and motivation, and provide a good opportunity to promote healthy eating amongst children and young people."
Under changes to school funding in England, schools now receive extra money for pupils who are receiving free school meals. This is known as the "pupil premium".
In Wales, there are plans to require local councils to provide free breakfasts for children if primary schools ask for them.
Mr Ireland says some children arrive at school hungry because for some parents, their children are "not their priority".
And although he supports the idea of schools providing free breakfasts, he says there is a danger that "the more we do, the more we will be expected to do".