Almost 90 per cent of parents have had to cut back or delay spending in order to pay the voluntary contribution charge to schools.
A new report from St Vincent de Paul has found the average payment per child is €140, with some schools charging as much as €550.
Out of 1,500 respondents, more than three quarters said it was not clearly communicated that the payments were optional.
Niamh Dalziel from SVP said the Government should intervene.
Ms Dalziel told Newstalk: "We want to see new regulations on voluntary and any other parents contributions. We want to see an increase in the capitation grant to ensure that schools can meet their running costs.
"We want to remove all financial barriers to participation for all pupils. We want to see poverty-proofing of all school policies across the education system."
