School funding in Northern Ireland is "on a precipice," according to a school head and union leader.
Graham Montgomery will tell an Association of School and College Leaders (ASCL) conference the system is "approaching the point of crisis".
The principal of Royal School Armagh is also ASCL president.
On Thursday, the Department of Education was told it faced significant cuts to its "current spending trajectory".
The warning was contained in the budget for Stormont departments set out by Northern Ireland Secretary Chris Heaton-Harris.
The Education Authority (EA), which has operational responsibility for the education system, recently warned it was facing a £300m deficit in its budget.
