Union members have vowed to take a strike into the New Year after a school sacked a teacher with a week's notice.
Sharon Morgan was the National Education Union (NEU) rep at London Design and Engineering UTC in Royal Docks, but lost her job after surveying staff wellbeing in the summer, according to the union.
All 19 survey respondents reported work-related symptoms of stress, the union says.
The union says there was no formal investigation or opportunity for Ms Morgan to appeal.
As a result of an interim employment tribunal the LDE management agreed to reinstate Ms Morgan - but backtracked a day later, according to the NEU. The Recorder understands the school continues to pay Ms Morgan's salary.
Jeremy Galpin, who chairs the LDE UTC Trust, said: "Our priority is always to provide a high quality education for our learners and we are saddened that the NEU has called a strike at what is such a critical time."
He added that seven out of 82 staff members are involved in the strike, and the college remains fully open with all lessons continuing as timetabled, except for any Covid-19 isolations.
NEU organiser Ed Lewis said: "If working hours remain too long and staff overworked, how good is that for pupils?"
The strikers want the school to reinstate Ms Morgan and make its contracts more secure so no one can be sacked at a week's notice.
Michael Gavan from the NEU said Ms Morgan was just doing her job as a trade union rep and members felt confident of victory at the full tribunal which is due in February.
"If they had taken Sharon back, we would not be in this situation," Mr Gavan said.
The strike began on December 1. Mr Lewis said there were hopes the school would agree to talks with the conciliation service, ACAS.
"If not, we may need to continue the campaign and strike action next year," he added.
Mr Galpin said: "We remain committed to further talks with the NEU in order to avoid further strike action as part of this dispute.”
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