Headteachers say growing numbers of parents are approaching schools to request financial support or help with essentials, and more children are “embarrassed and ashamed” by their family’s poverty.

In a survey by the National Association of Head Teachers, three-quarters of school leaders said they had seen an increase over the last five years in the number of parents seeking help, including advice on how to access foodbanks and other welfare support.

In several cases schools said they had set up their own foodbanks to tackle food poverty. But nearly 90% of headteachers said they were not able to sustain their current level of support for disadvantaged families, given the pressures on their budgets.

One in five said they had seen an increase in the number of children coming to school hungry.

One headteacher, from east Birmingham, said: “This year has seen additional strain and emotional distress for children as we have seen families being evicted and made homeless. This has not been the case in my 20 years at the school, but in the last two months five families have been impacted upon in this manner.”

Another, from Derbyshire, said: “I’ve seen a pupil eat a biscuit for breakfast and have a mouldy piece of bread as their only lunch in their box – and have parents break down when confronted as they haven’t eaten all day either.”

Another head, from Brent in north London, said: “Children are hungry, so we feed them breakfast and lunch and run a foodbank. Otherwise they cannot learn. Families are living in one room in shared houses with several other families. Families are sharing a bed. This means children are not getting a night’s sleep. Children are embarrassed by their clothing, so they act out or appear withdrawn.”

Judy Shaw, the NAHT’s president, said: “I call upon our government to lift their eyes from their Brexit dossiers, look around them and offer recognition, understanding, compassion and immediate support. Don’t leave it to schools to pick up the pieces alone.”

The education secretary, Damian Hinds, addressed the NAHT’s annual conference in Telford on Friday, saying he was determined to extract more funding from the Treasury in the forthcoming spending review.

Asked why he had not raised teachers’ pay, as recommended by the government’s advisory body, he said he did not “want to put more financial pressures on to schools”.

The Department for Education announced a £10m package for schools needing to improve discipline, include funds for consultations with the behaviour guru Tom Bennett.

Hinds also said school staff needed greater protection from parents on social media. “While attention is mainly focused on protecting young people from possible online danger, they are not the only victims. Teachers and leaders can be vulnerable too,” he told journalists.

“Teachers and leaders simply should not be subject to online abuse simply for doing their jobs and I’m 100% behind making sure the entire school workforce go about their business free from intimidation. No teacher should have to put up with sometimes vitriolic comments, and we need to make sure they are protected for that.”