The Children's Rights Alliance says the lack of choice in schools is likely to come under renewed scrutiny in January, when Ireland's rights record is examined.
The group has compiled a report on children's rights for the UN Committee on the Rights of the Child, and finds that while progress has been made in recent years, more work needs to be done.
One area of concern is the lack of school choice in many parts of the country.
Marie Corbett, the legal and policy director with the Children's Rights Alliance, said: "The UN has criticised Ireland in the past in relation to our education system and we expect they will examine this issue again.
"The issue is that the majority of schools in Ireland are denominational, they have a religious patron, so it is very difficult for families that have either a different religion or wish their child to be educated in a multi-denominational context.
"The lack of choices in schools is a huge problem."