NEU union members at St Catherine’s School for Girls struck on Tuesday of last week in a row over bullying.
It was the latest walkout in a series of escalating strikes that began on 30 October.
Workers at the Bexleyheath school in south east London say the head teacher has targeted union activists and banned union meetings.
In a statement, the union said that an NEU rep at the school was “unfairly suspended based on a fake allegation” in June. “The member of staff concerned was suspended for four and a half weeks and reinstated with no case to answer,” it continued. “Suspension is a potentially career-damaging action and the union believe it has been used by the school to bully staff into silence.”
The NEU said that a “culture of fear” exists at the school.
It said the head teacher and chair of governors have written to parents five times, attacking school staff.
It said this is “indicative of the bullying behaviour of the leadership of the school”.
Greenwich & Bexley TUC has appealed for supporters to invite strikers into their union meetings to build solidarity for the dispute.