NEU union members at The Barclay School in Stevenage, Hertfordshire, struck on Wednesday 12 December.
They are fighting a plan for the school to become part of a Multi Academy Trust (Mat) this month.
The school faces being taken over by London-based MAT Future Academies Trust, chaired by Tory and former schools minister Lord Nash.
The Department for Education (DfE) ordered it to become an academy after it was rated inadequate by Ofsted in 2016.
Parents are also campaigning against the academy plan. A group of parents delivered a petition signed by over 1,500 people to the DfE on 10 December.
Parent Jane said she hoped that education secretary Damian Hinds would “confirm that the wish of our community is listened to, and the academy order on Barclay School be revoked”.
Herts County Council councillor Joshua Bennett Lovell joined parents.
He called the academy order “an unnecessary distraction”.
And he called a protest outside the school in support of NEU members on the day of the strike.
Teachers could strike over pay in England and Wales
An indicative ballot over pay in the NEU education union is set to end early this month.
The School Teachers’ Review Body had recommended a 3.5 percent pay rise for all teachers.
Yet the government refused to implement this.
Instead it has said that only teachers on the main pay scale, around 40 percent of teachers, will get 3.5 percent.
The rest will get 2 percent and school leadership will get 1.5 percent.
The government has also refused to fully fund the rises.
This means schools that are already suffering cuts will be expected to fund part of the rises themselves. The ballot asks whether members would support industrial action to win better funding for schools and to secure the recommended pay award.
At a rally in central London last November, joint general secretary of the NEU Kevin Courtney called for the “biggest yes vote in the ballot”.
He thanked politicians, including Labour leader Jeremy Corbyn, who have pledged their support for teachers.
He added, “But it’s our actions that make the difference. It’s time for us to fight back.”