Barnardos says the government must do more to ensure equal access to education for all children regardless of their parent's income.
In its annual school costs survey, the children's charity found that poorer families are unable to afford basics such as books and uniforms.
Barnardos says costs far outstrip the State's Back to School Clothing and Footwear Allowance, which is currently worth €100 for a primary school child, and €200 for a child at second level.
However, it notes that book schemes and cheaper uniforms have gone some way towards easing the burden.
Fergus Finlay of Barnardos says the education system in Ireland is far from free.
"If you're starting a child in primary and perhaps another in secondary school, you're going to have to find about €1,200 between now and September for uniforms, footwear, schoolbooks, classroom resources, and the 'voluntary' contribution," he said.
"For a society that regards education as a constitutional right, that's a million, million miles away from free education."
He also called for increased access to the back-to-school allowance with wider bands in the means testing.