Schools are predicted to be millions in the red in the next three years. The overall education budget, announced in the summer, is £24 million less than the closing 2016/17 budget.
While an additional £10 million was found after the reallocation of cash across Stormont departments, heads are yet to see a penny.
Unions say cuts mean schools will find it impossible to maintain their high quality of education.
Northern Ireland’s budget for 2017/18 was published last week and shows an increase in education spending of 1.5 per cent.
The Irish National Teachers’ Organisation (INTO) says this 1.5 per cent is “in reality another cut given inflation is running at almost four per cent”.
INTO northern secretary Gerry Murphy said: “The education system in the North now finds itself in dire straits. Eighty per cent of our schools will find themselves in a negative financial situation at the end of this financial year. We will quickly now begin to see a rapid increase in class sizes. In addition, services necessary to support the learning delivered by a shrinking, overworked teaching profession, will be reduced further.
“Principal teachers and volunteer school governors are increasingly finding themselves having to take decisions that are placing them in the role of gate-keepers.”
NAHT’s Northern Irish president Paul McClenaghan says that while his union welcomes the increase in principle, it is concerned it “merely constitutes a reframing of the budget and will not have an impact on the cuts”.
“What these budget reductions equate to in practical terms are staff cuts, larger class sizes, and cut backs in support for children with additional needs,” he added.
“As a consequence, further pressure is placed on parents to subsidise resources. Essential school maintenance and refurbishment of buildings to meet the growing demand of the school population has become impossible.”