The ASTI is to ballot its 17,000 members on the Junior Cycle reform proposals, after its Central Executive Council met in Dublin this afternoon to discuss changes to the cycle.
The union has said proposals to overhaul the junior cycle exam system include a number of "educationally unsound" reforms that had the potential to damage young people’s education.
Minister for Education Ruairi Quinn plans to remove external examiners from the Junior Cycle in exchange for continuous assessment carried out internally by teachers.
ASTI General Secretary Pat King said that teachers' concerns had not been addressed.
"Teachers want to do this right," he said. "Students have one chance to go through the school system. It must be right.
"Teachers are worried standards will vary between one school and another because the Minister has decided to remove the state examination system at junior cert level."
If implemented, the new Junior Cycle Student Award will be phased in from next September.
ASTI members are now to be balloted on withdrawal of cooperation and on industrial action. The TUI union has already voted in favour of balloting its members.