POST-PRIMARY principals have warned of a crisis due to a lack of money.
In a letter, the school heads said they were united in their concern about "inadequacy of the current funding".
Many schools are struggling to stay in the black.
Although this year's education pot increased by 4.3 per cent, this is only when compared to last year's baseline budget. An extra £80m was found during the year.
Principals have now outlined their concerns in a letter to the Education Authority (EA), Department of Education and MPs.
Signed "every post primary school principal in Northern Ireland", it states that they are being required to "make excellent teachers redundant during a time of ongoing and increasing industrial action".
"Underfunding has been a sustained pressure in the post-primary sector for the past five years and is now affecting all post-primary schools. Parents should be aware that the quality of education provided will inevitably be impacted by the reduction in teacher numbers and the associated unacceptable levels of pressure on serving teachers and leadership teams in schools," it says.
"We are now asking for some immediate action to rethink the allocation of the defined budget for education. This includes a complete restructuring of the amount of money which is absorbed by non-frontline services and a greater delegation of funds to post-primary schools."
EA chief executive Gavin Boyd said it was "very evident" that there is not enough money to run the system as currently structured.
"We have been providing support to individual schools to help develop their financial plans over the last two months. It is very clear that for a significant number of schools, whilst they are doing all they can to reduce costs, there is little possibility of living within their budget without seriously impacting the quality of teaching and learning in the school," he said.