Some children who have been expelled from school for poor behaviour may not be receiving any formal education, the State body with responsibility for monitoring school attendance has acknowledged.
The National Educational Welfare Board said it only had statistics for the number of children expelled over the past two years and as a result it could not say how many children in total were now out of school.
According to the board's statistics, last year seven children were expelled at primary level, while 68 children were expelled at post-primary level.
Eddie Ward, chief executive of the board, said it was working to introduce a system to allow it to track what happens to students who are expelled or who have left school for another reason.
"Our worry at the moment is that those children who were out there before we took over are not being recorded," he said. "But we would be quite confident that we are being notified of students who have been expelled from schools since we took over in the past two years."
The majority of these students would be 16 years of age, although some would be younger, Mr Ward said. Children of immigrants were also at risk of dropping out of the school system without being detected.
However, 8,000 cases of non-attendance were resolved by the board last year, he added.
A conference organised by the board on alternatives to the "last resort" of fining or imprisoning parents of children who are not attending school, yesterday heard that parents cite large class sizes, bullying, and their own lack of literacy as reasons for their child's non-attendance at school.
Some children also think their parents are a "soft touch" and use this to get parents to agree to their absence. Others experiencing difficulties with individual teachers "mitch" to avoid class, but end up staying out of school all day.
Catherine Bond, the board's regional manager for Dublin city, said parents had told it class sizes could be so large that teachers "are not sorry if disruptive children are absent".
Parents can find it humiliating when they cannot help children with their homework because they are unable to read or write, she said. Traveller parents also talked about the pointlessness of education when jobs will not be given to Travellers anyway.
But parents also suggested that a "boot camp" might be introduced for those parents who do not support their child, while other suggestions included making parents sign their child in and out of school.
Recommendations from yesterday's conference, along with further consultations with parents, will form the basis of a "progressive" option open to judges faced with school attendance cases.