Teachers at The John Roan school in Greenwich, south east London, held a silent picket outside the school on Thursday of last week.
NEU union members had planned to strike on the day, as part of a long-running campaign to stop the school becoming an academy. But the union suspended strikes after Labour-run Greenwich council threatened legal action.
However GMB union members at the school were set to strike this Thursday. Teachers said they would not cross the picket line.
Workers fear that a takeover by the UST chain could see subjects cut and top bosses grabbing huge salaries.
They have appealed for people to contact the chair of governors and National Schools Commissioner Dominic Herrington to oppose the plan.
Teachers and parents were celebrating last week after Sherington primary school scrapped plans to turn the school into an academy.
GMB and NEU union members at the school in south east London had called six days of strikes against the plan. Governors there met on Wednesday of last week and unanimously voted to keep the school run by Greenwich council.
In a letter, governors said the best way to provide financial stability and retain staff was to stay as part of the local authority.
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