Teachers 'paying for resources out of own money'
One in five teachers is using their own money to buy classroom resources once a week, a survey by the NASUWT suggests.
And 45% of the 4,386 members of the teachers' union surveyed said they had bought essentials such as food or clothing for pupils in the last year.
The survey comes as about 7,000 head teachers in England wrote to parents before the Easter holidays highlighting what they call a "funding crisis".
Ministers say school finances are a priority for the next spending review.
"We are told there is no money for anything, all departmental budgets have been frozen and all the stockrooms are empty," one teacher responded in the study.
"Basic resources are rationed out at the beginning of each term and once they are gone, there is no more unless you purchase them yourself."
Another said: "I've had to purchase small tables, CD player, outdoor provision and storage."
One teacher said: "Small amounts do add up during the year, all departments are feeling the pinch and books/texts (English GCSE included) are now shared for reading in lessons and not allowed home as they used to be.
"We cannot afford for items to be lost - so we deprive students of the chance for self-directed study for those who are motivated."
Another commented: "Last time my lesson was observed, by a senior leader, I was graded low for lack of relevant resources - despite having spent £20 on stuff.
"The expectation is we purchase things ourselves as our job is a vocation! I'm fed up of hearing this over and over again. It's never enough and am ready to leave."
Pupils in need
The NASUWT survey, which is published ahead of the union's annual conference in Belfast over the Easter weekend, covers both primary and secondary schools and also found that teachers were paying for basic necessities such as food, clothing and toiletries for pupils.
One teacher said: "The worst thing to experience as a teacher is watching a hungry child who is in receipt of free school meals, having to stand and watch their friends eat breakfast before school or have snacks at morning break when they are hungry.
"Typically, I have used my credit on the prepayment system to give children cheese on toast or a hot drink, or any other hot food."
Another said: "I have paid for and supplied materials to resole or repair shoes. Pupils regularly come without the basics such as a pencil to write with."
Chris Keates, general secretary of the NASUWT, said that teachers were "shouldering financial burdens to support their pupils".
"Teachers care deeply about the pupils they teach and will go to great lengths to ensure their needs are being met," she said.
"Teachers once again are being left to pick up the pieces of failed education, social and economic policies."
But children's minister Nadhim Zahawi said there was "more money going into our schools than ever before".
"However, we recognise the budgeting challenges schools face and have introduced a wide range of practical support to help schools and head teachers make the most of every pound on non-staff costs."
Tackling disadvantage was a "priority for this government", he added, which was why "we are making sure that more than a million of the most disadvantaged children are also accessing free school meals throughout their education".
In his budget in October last year, Chancellor Philip Hammond announced that schools in England would receive a one-off £400m - on average, £10,000 per primary school and £50,000 per secondary school - to buy "that extra bit of kit".
However, his words provoked an angry response among some teachers and parents on social media, who said he was out of touch.
There have been repeated concerns from schools about funding shortages, with the Institute for Fiscal Studies showing in July last year that per pupil spending had fallen in real terms by 8% since 2010.
Earlier this year, the Education Policy Institute said that almost a third of local authority secondary schools in England were unable to cover their costs, with the proportion of these schools in the red almost quadrupling in four years.
The WorthLess? campaign group, which is made up of head teachers across England, has been campaigning for better funding for schools.
The group sends letters to parents and carers setting out their concerns and has protested at Westminster.
Their latest letter, sent at the end of term, was circulated by some 7,000 head teachers.