Many parents (76%) in England, Wales and Northern Ireland say the cost of sending their children to school is rising, a poll by Parentkind suggests.
The charity's annual survey found most (51%) of the 1,500 parents polled were concerned about the cost.
The cost of uniform was the most common concern (46%), followed by school trips (44%) and school meals (19%).
Almost two-fifths (38%) of the parents had been asked to donate to a school fund this year.
Of those that have donated to these funds, about a quarter (26%) said they gave more than £10 a month.
Of all the parents surveyed:
- 22% had been asked to pay for school clubs that used to be free
- 20% had been asked to pay for events such as sports day or concerts
- 16% had been asked to supply teaching equipment
- 11% had been asked to help with maintenance activities such as redecorating classrooms and cutting grass and hedgerows
- 6% had been asked to supply essentials such as toilet paper
The survey, conducted before £7.1bn extra funding for schools in England was announced by Prime Minister Boris Johnson, in August, asked parents how any additional money given to their child's school should be spent:
- 55% said it should go on learning resources such as textbooks and science equipment
- 43% said IT equipment.
- 39% said child mental health services
- 36% said maintaining school buildings
- 36% said school trips
- 34% said pupils with special educational needs and disabilities
Parentkind chief executive John Jolly said: "These findings clearly show that parents are worried about the increasing cost of sending their child to school and the impact that squeezed budgets are having on the day-to-day delivery of a good education.
"Schools should regularly engage with families to fully understand the challenges they face - many already do this well.
"But, no school funding decision that impacts directly on the families in their community should be made without consultation and particularly if it increases the financial burden placed on parents or results in the unintended consequence of mums and dads participating less in their child's education."
National Association of Head Teachers general secretary Paul Whiteman said: "Parents and carers are not the only ones who worry about austerity.
"Tragically, children are well aware of their family's money troubles.
"Our members tell us that children's worries leave them unable to learn and enjoy school - they are often embarrassed and ashamed.
"It's a message that sticks in the throat of everyone who has young people's best interests at heart."
A Department for Education spokeswoman said the extra funding announced last month would mean all secondary schools in England would level-up to at least £5,000 per pupil next year and primary schools would receive at least £4,000 per pupil by 2021-22.