North London school pupils were reportedly forced to wear coats and hats in lessons so their cash-strapped school could save money on heating bills.
Children at the same school have also gone without textbooks and have been banned from using the photocopier, a prominent education campaigner said.
She added that the issues have come about as teachers battle with tight budgets and funding deficits.
Jo Yurky, co-founder of the Fair Funding For All Schools campaign, laid bare the effect of Government spending cuts on frontline teaching at the National Union of Teachers (NUT) conference in Cardiff on Saturday.
The 41-year-old, from Haringey, told delegates: "In one secondary school near me, the children were taught for the first two weeks of January with their coats and hats on because they've had to be a bit more careful about when they turn the heating on, to save money.
"That school can't afford to buy textbooks that the pupils need, but they also can't afford to photocopy them because that budget's been cut too.
"A primary near me had to cut a teaching post, a teaching assistant post, its music club and its science club to save money."
She added: "If you look at the DfE's website, they tell schools how to make efficiencies. And so some schools, in trying to make efficiencies, they don't turn the heating on so much.
"It's not on over the school holidays, over Christmas, the children come back and the school's freezing.
"It's a school where they don't have funds to buy textbooks, they can't photocopy textbooks, they ask parents for money.
"Who would want their child to be in that classroom? Nobody. How does it help the child to learn? It doesn't.
"This is the state of things because there is a significant financial problem with our schools."
Ms Yurky, a former parliamentary ombudsman and now a registered childminder, said another school, Latymer grammar in Edmonton, sent begging letters to ask for charitable donations.
The school managed to raise £80,000 to help patch up a £300,000 shortfall.
"It's money they use to balance the books," she said.
"This is an ongoing fundraising appeal. They raise a certain amount and then they ask for more.
"That school has also cut a history post, half an English post, and four subjects from its A-level (programme).
"Since time began, PTAs (Parent Teacher Associations) raised money for the extras for our children through cake sales.
"This is in addition to that - those parents are now asked to make a monthly contribution, per child, until they leave the school."
She said parents are concerned that they are unable to plug the funding deficits, and that - as a business model - it is unsustainable.
She said: "Of course parents want to support their schools, but there aren't many of us who have much money to spend at the moment.
"We do give a lot already, where we can.
"We think it's an extra burden. It makes you feel, if you don't contribute, will you be looked upon less favourably?
"But we also think why is there a problem with money? The Government says funding is protected. We would rather the Government talked to the schools and sorted out the problem."
It came as NUT members signalled their intention to organise a one-day strike across parts of England before the end of the school year over a perceived lack of funding.
Additional reporting by Press Association