Almost half of the parents of WA public school students failed to pay their school fees last year and principals fear this further disadvantages students from poorer areas.
They say a major review of the voluntary fee system is needed.
Public schools can ask for up to $60 for each primary school student and $235 for students in Years 8-10.
The payments, which have not changed in 11 years, go towards materials and services students use such as stationery, art materials, textbooks and photocopies.
Education Department figures show that on average, 53 per cent of high school parents and 56 per cent of primary school parents paid the fee last year. A school-by-school analysis reveals parents in well-off suburbs and small towns were more likely to pay than those in disadvantaged areas.
More than 90 per cent of parents of students at Nedlands, Wembley and Bencubbin primary schools paid, compared with only about one-third of parents of students at Belmont, Bentley and Tapping primary schools.
WA Primary Principals Association president Stephen Breen said some public schools had widely different funding, which was unfair.
"What we're actually saying is that the whole system needs to be looked at because of the inequities," he said.
Mr Breen called for a wider community debate on whether education was really "free".
"We all know that it's not free, but some people use that excuse, 'I'm not going to pay it because it's free education'," he said. "It needs to be talked about because it's quite illogical in the 21st century."
Options could include abolishing fees, making them compulsory or increasing the primary school payment in line with high schools.
WA Secondary School Executives Association president Rob Nairn said principals were concerned that some schools could not deliver programs equivalent to those where nearly all parents paid.
He said the high school fee had been capped at $235 for more than a decade but education costs had risen significantly over that period.
"It's probably about time we had a review and an open discussion around the cost of education and whether or not there should be compulsory charges," Mr Nairn said.
Premier Colin Barnett made secondary school fees compulsory in 2001 when education minister but the Gallop government overturned the move just months later.
Asked whether he would consider compulsory fees, Education Minister Peter Collier said some schools collected more than others but schools worked with parents to inform them about the important areas the money went to.
"Families have many household costs but the fees requested are modest and do not reflect anywhere near the cost of a high-quality education," Mr Collier said.Shadow education minister Sue Ellery said the rising cost of living was hurting parents who had to prioritise their spending.