17,000 secondary school teachers are to take industrial action after rejecting the government's proposed pay deal.
63 per cent of members of the ASTI have voted to reject the Haddington Road agreement, which would abolish some of their allowances.
Another 14,000 teachers may join them when the results of a similar ballot by the TUI are announced later this afternoon.
ASTI president Sally Maguire says the ballot sends a clear message:
