Paul Gosling, president of the National Association of Headteachers union, said: "The government knows that when kids turn up in the morning hungry and cold, schools will step in and help. But it's not right that it's being left to us with no extra support."
He said that with huge energy bills and an unfunded teacher pay rise, supporting desperate families would push hundreds of schools into deficit. Headteachers welcomed the government's announcement last week that electricity and gas in schools would be capped at a lower "government-supported price", knocking off £4,000 for a school paying £10,000 a month for energy. But they expressed anxiety that the cap is only being offered for six months, and warned that many schools will still be left with much higher bills than they budgeted for.
Will Teece, headteacher at Brookvale Groby Learning Campus, a secondary academy school in Leicester, said parents had been ringing, asking whether the school would be offering free breakfast clubs or after-school clubs with food included.
He warned: "At a time when there is much greater need for support for our families, we are in a much weaker position to be able to provide it."
Oxford Mutual Aid, a community group which delivers emergency food parcels, has had to cut its delivery days because its hundreds of volunteer packers, drivers and organisers cannot cope with the increase in requests for help, which include regular referrals from primary schools.
Coordinator Muireann Meehan Speed said: "We are struggling to keep up with the demand. Every day I hear the level of distress people are in. Every day I talk to scared families who don't know where to turn. But we can't do more than we are already doing."
The group is hearing daily from local people who have never been unable to afford food before. "They aren't choosing whether to heat or eat: they can't afford to do either," she said.
Craig Johnson, founder of Launch Foods, a charity in Glasgow providing free lunches for 300 schoolchildren a day, said: "People are talking about an approaching crisis. There is already a crisis."
The charity, which drives silver trucks into primary schools and feeds everyone "with no stigma" using surplus food, has had to take its phone number off its website because it was receiving daily calls from people in places including Newcastle, Liverpool and London, asking if they could help feed children in their area.
"I am getting so frustrated, telling people we can't help them," Johnson said. "There shouldn't be a kid in England, Wales, Scotland or Ireland going hungry. It's just wrong."
Michelle Dornelly, founder of Children with Voices, a charity that is feeding families on three estates in Hackney, east London, said they are struggling to cope with "a different level of need".
As well as children regularly going to bed hungry, she is worried about their growing anxiety levels. "I'm concerned about children going to school with no pens, no deodorant, no toothbrushes. All that affects self-esteem, and their self-confidence is really flagging."
Dornelly, who is on universal credit herself, says her charity doesn't have enough storage space or freezers, and she worries about how much her women volunteers are taking on. "I love what I do, but I feel angry that we are left to do this without help from the government," she said.
"MPs should come and walk the streets of Hackney and find out what is going on."
"No child should come to school too hungry to learn. No one can accuse this of being a "radical" statement but, in 2022, childhood hunger is a shocking reality in millions of families. We are facing the worst cost of living crisis in a generation and wages are not keeping pace with rising bills. Neither are benefits. This is hitting the most vulnerable the hardest. Latest statistics show 3.9 million children – eight in every class of 30 – are growing up in poverty. Some 2.6 million children live in households that have gone short of food in the last month," Kevin Courtney said in a video shared on the website of the British daily Mirror.
"Children have started the new school term in the midst of the greatest cost of living crisis in a generation. Child poverty numbers are creeping towards four million as the cost of food and fuel spirals. Shamefully, we are witnessing the re-emergence of Victorian illnesses like rickets. Something must be done.
We are facing the worst cost-of-living crisis in living memory. Wages and benefits aren't keeping pace with rising bills. This is hitting our children, the most vulnerable members of society, the hardest.
Regular, nutritious food is the backbone of a secure childhood – and vital for ensuring every child can reach their potential in school. But too many young people are going without – 2.6 million children live in households that have gone short of food in the last month.
No child should come to school too hungry to learn. No child should have to experience anxiety or fear for where their next meal is coming from. No child should feel humiliated by their families' circumstances, or struggle to concentrate in class because they haven't had lunch. But now, in 2022, this is the shocking reality that millions of children are enduring," The National Education Union pointed out.