Gerry Murphy was speaking at the annual northern conference of the INTO union in Newcastle, Co Down.
Mr Murphy said the vote by people in England and Wales to leave the European Union will bring about significant negative consequences for everyone.
He claims the Department of Education and employing authorities seem more concerned about balancing budgets than meeting the needs of children and young.
“In purely economic terms we will lose £250 million out of the local economy, agriculture and the voluntary and communities sectors in particular will suffer,” he said.
“There is a distinct possibility following the divorce that the British government will have to pay hundreds of millions back to Brussels not to mention the additional tariffs imposed on goods to be exported from the UK to the markets in the European Union.
“We will continue to campaign for a solution to the issues of pay and workloads. Brexit consequences are not good for teachers.”
The conference also focused on a long-running pay dispute which has seen INTO members stage one strike with a second day planned later this month.
Mr Murphy says the huge turnout in the INTO’s strike ballot gave an emphatic mandate to the northern committee to carry out a refreshed campaign of industrial action.
“This is unprecedented and it begs the question how can a handful of politicians and bureaucrats be right about how the education system is to be run when the entire teaching workforce in their employment is in open revolt,” he continued.
“I say again, if the money owed for 2015/16 is paid, action can be avoided. We will have to take further action and I am confirming a half-day strike action to take place on the afternoon of March 23.”