Parents of second-level students have said further cuts to education will push schools to breaking point.
In its pre-budget submission, the Post-Primary Education Forum (PPEF) said the increase in pupil-teacher ratio had already had a devastating impact on schools.
The PPEF warned that with 30,000 extra second-level pupils expected over the next few years, cutting the education budget would have a long-term impact.
Spokesperson for the group Tommy Walshe said it was not just about one more pupil in a classroom.
"They don't look at the cuts in subject choices, or where you have pass level and honours level being taught in the one classroom. One pupil doesn't mean one pupil - you have to look at the big picture," he said.