Government backbenchers have warned of the extra cost to the taxpayer if more private schools go public.
It's reported today that 12 of the country's 55 private schools are looking to move into the public sector.
The move would mean the education budget would be spread over a larger number of schools, at a time when less money is available.
Labour's Aodhan Ó Riordáin says adding more schools to the public system would increase the burden on the state:
Private schools have seen their enrolment numbers fall in recent years, as fewer families can afford the fees of sending their child to a private school.
The pupil-teacher ratio in private schools is being increased this year - the ratio will now stand at 23:1, compared to 19:1 in secondary schools in the public system.
One private school, the Church of Ireland-ethos Kilkenny College, has already taken the decision to move to the public system and will begin taking public pupils when it opens for 1st Year students tomorrow.