School waiting lists are being phased out.
It is mainly going to affect fee paying secondary school pupils - many of whom have their names down 10 years in advance.
The changes were originally due to come into force from September, but they have been delayed until next year.
Arthur Godsil, the former headmaster of the private St Andrew's College in Dublin, said it may cause a problem for schools that have already taken deposits from parents.
“I’m not a lawyer but I believe that some schools have taken legal advice on this and I believe that there is an issue there.
“And I would be very sympathetic to parents who put their children’s names down ten years ago or more - only to be told, ‘sorry, you’ve been bumped off’.
“That’s something that needs to be addressed.”