Nearly 400 government teachers in Tonga are planning to go on strike next week.
The Public Service Association Assistant Secretary Mele 'Amanaki says its members believe they are being punished for taking part in last years civil servant strike.
Ms 'Amanaki says the treatment of the teachers is against the memorandum of understanding which ended the strike, which said no one would be disciplined or discriminated against for taking part.
She says teachers who are eligible and deserve promotions are being overlooked for people who did not take action last year.
Ms 'Amanaki says others are being transferred to smaller schools.
"Some of the staff who were on strike, especially those who were active in the interim-committee, they have been transferred to the outer islands. Normally if somebody is transferred to the outer islands, literally going to the same post they were in, it's seen as a demotion."
Mele 'Amanaki says the strike will begin on Monday if there is no response to their concerns from the government.
She says the PSA is also ready to take legal action for breaching the MOU.