The Department of Education has published an analysis of the fee income received by Ireland's 55 private second-level schools.
It found that the schools share more than €80m in additional income between them every year, compared to similar sized schools outside the fee-charging sector.
The top nine fee-charging schools have an average disposable income of more than €2m annually, compared to schools that do not charge fees.
The 29-page report was commissioned just over a year ago.
It estimates the day-to-day finances of the country's private State-aided schools and suggests a sector in a healthy financial state.
Fee-charging schools benefit from additional incomes of up to €4.7m each annually.
This amounts to an additional income of between €1,300 and €8,600 per student.
The report also calculates that if all the country's fee-charging schools decided to enter the free education sector it would cost the State €23.5m in additional funding.
The Department of Education report was compiled using data supplied by individual fee-charging schools.
The department said it will now be used to inform public policy.
Minister for Education Ruairi Quinn said society needs to look at how best it can utilise its scarce resources.
The minister said the report showed the 55 fee-charging schools had a lot of money between them.
If there were to be changes in the allocation of resources, he said, now we have a clearer picture of what was out there.
Mr Quinn said as Minister for Education in difficult times he had to make the resources available to him spread as far as they possibly could.
The Teachers' Union of Ireland has said Mr Quinn should call for funds to be re-diverted to disadvantaged schools.
TUI General Secretary John MacGabhann said all students should share an equal playing field.
Representing schools in the fee-charging sector, Joint Managerial Body General Secretary Ferdia Kelly said it was important to remember that the more than €80m referred to in the report was money contributed by parents, not the State.
Speaking on RTÉ's News at One, Mr Kelly said: "What the State is simply doing is paying for teachers to teach the students.
"If those students were in the free education sector the State would be paying them.
"7% of students in second-level happen to be in the fee-charging sector. The State simply pays for the teachers to teach them.
"There's no other top-ups, no other subventions, no other grants. There's nothing else going into the fee-charging schools."
Referring to the country's Protestant fee-charging schools, Mr Kelly said it was vital that the State continued to support them in providing Protestant education for young people whose parents wished it.