School leaders' union NAHT NI has responded to a letter from the Education Authority revealing a £300 million funding gap and asking schools to restrict spending, including on substitute cover and new appointments, saying it demonstrates the impossible nature of running schools in the current financial climate and confirms the crisis that school leaders have been talking about for years.

The letter, sent to all school principals, states that "unlike the position in previous years, we have been advised that no further significant funding allocations are likely to be made available" and that the sector is "currently on a trajectory towards a significant overspend at year end."

Schools are being asked to restrict substitute cover, minimise new appointments, avoid discretionary spending and not use accumulated surpluses. The letter acknowledges that the sector is "living with the consequences of years of increasingly unmanageable funding shortfalls" and that warnings about this year's budget "are sadly being borne out by events."

Dr Graham Gault, NAHT NI national secretary, said: "This letter from the Education Authority lays bare the dire financial reality facing our schools. A £300 million funding gap with no prospect of additional funding represents an education emergency. It is the direct outworking of political choice - both at Westminster and in Stormont - and it is our children who are paying the price.

"School leaders have been warning for years that children in their schools are being failed as a result of political choices not to fund education adequately. This letter confirms everything we have been saying. The situation is now critical, and our children cannot afford this level of failure any longer.

"The Education Authority's own letter acknowledges 'years of increasingly unmanageable funding shortfalls' and admits that warnings about this year's budget are 'sadly being borne out by events.' In other words, this was entirely foreseeable and entirely preventable.

"We are now in a position where schools are being asked to restrict substitute cover when teachers are absent. What does this mean in practice? It potentially means children losing out on their education, larger class sizes school leaders and teachers being stretched even thinner trying to cover gaps. It definitely means further damage to an already overstretched workforce.

"Schools are even being asked not to use their own accumulated surpluses - money they have carefully managed and set aside. This demonstrates just how catastrophic the financial situation has become.

"School leaders are tired of hearing politicians talking about how much they value education when political choices are consistently made to not fund education adequately. The warm words ring hollow when schools are being asked to operate in crisis management mode because there simply is not enough money to provide children with the education they deserve.

"This is not about schools being inefficient or wasteful. This is about a system that has been systematically starved of resources through deliberate political choices over many years. School leaders are being asked to make impossible decisions that will inevitably impact on the quality of education we can provide to our children.

"We need to see political choices made to direct significant and meaningful money to frontline education immediately. Not in a few years. Not when budgets allow. Now. The Independent Review of Education has estimated that Northern Ireland needs an additional £291 million to close the school funding gap with England and Wales. This Education Authority letter confirms we are now facing a £300 million gap for this year alone. That is the scale of the crisis we are in.

"School leaders have been managing decline for far too long. Our children deserve better than this. They deserve political leaders who will prioritise their education and their futures over political point-scoring and empty rhetoric.

"As I have said before, people need to ask politicians repeatedly: Exactly how will you ensure that funding is fully restored directly to our schools immediately? Do not accept any failure to answer this question. Our children's education depends on it."