Parents at the launch of the NCPTAreport this week claimed that they are being blackmailed into paying Pounds 1.2 billion for their children's schooling.
They said that weekly cash demands for Pounds 3 or Pounds 4 are being made by schools in letters requesting parents' permission for their children to take part in activities. Refusal to pay up can lead to events being cancelled for the whole class or their child being left out.
One told a story of a Year 8 girl who asked her parents to keep her off school for three days rather than be identified as unable to pay the Pounds 20 her grant-maintained school in Kent was asking for an arts week. The alternative was being forced to work with pupils a year below her while her classmates took part in arts activities.
The accusations of blackmail came as the NCPTA's report revealed that parents are propping up state schools to an extraordinary extent. It shows that they are raising Pounds 77 million through fetes, barbecues and sponsored events, while schools themselves bring in another Pounds 51 million through voluntary parental contributions and covenanting schemes.
The Pounds 1.2 billion for trips and activities associated with the national curriculum is on top of that and excludes money for school dinners.
Sean Rogers, chair-elect of the NCPTA, called at the launch for an end to what he called the unofficial parents' tax - even if it means paying more in income tax.
"Parents know education has to be paid for," he said. "But they would rather pay an honest tax than have their arms twisted behind their backs week after week to pay for the extras that schools demand. They would rather that the Governmentwas honest about what is going on."
Parents complained that they were bullied into shopping at certain stores in order to collect vouchers for computers and that they were fed up with having to put their hands in their pockets for textbooks and equipment.
Judith Wood, a mother of five from Norfolk, said: "My children will only get one chance at their education. I know I am going to be blackmailed but I want the best for them."
She said that demands came particularly for money to support technology lessons. For cookery lessons she sent in not only ingredients but also cash.
"I am stopping short of sending in a computer," she said at the launch of the NCPTA report this week, "but I am collecting my vouchers."
Ian Barker, head of St Edward's C of E primary in Rochdale, said: "Schools are being put into an invidious position where they have got to do it. In short, it is controlled blackmail.
"There are requirements in the national curriculum that say children have to have an activity experience, and the only waythe school can fund it is eitherby going to the PTA or asking parents for voluntary contributions."