Parents and teachers at one of the oldest state schools in the country have become the latest to take up the fight against plans to remove their school from local authority control and force it to become an academy.

The John Roan school, which has been teaching children in Greenwich, south-east London for more than 300 years, was made the subject of an academy order earlier this year after an Ofsted inspection found it was “inadequate”.

About 60 teachers at the school, who belong to the National Education Union (NEU), walked out on Wednesday for their eighth day of strike action supported by parents of some of the 1,200 pupils, under the campaign banner John Roan Resists.

They are opposed to the school being taken over by the University Schools Trust, which has been named as the preferred sponsor. More than 1,000 people have signed a petition and 300 families from the school have written to the chair of governors raising concerns about the financial viability and suitability of UST to run the school.

They want to see Ofsted reinspect the school and the academy order revoked. “We all agree that the school has already seen improvements – we should be allowed to continue to work together without the disruption that academisation would bring,” the letter says.

Kirstie Paton, a social sciences teacher and union representative, has worked at the school for 18 years. “We are concerned an academy trust will come in and destroy the inclusive nature of the school and narrow the curriculum,” she said.

Kes Grant, a Church of England priest who has three grandsons at the school, agrees: “We are very committed to community education that’s accountable to the local authority and to taxpayers.”

Not all parents are supportive of the strike. More than 100 have signed a separate letter expressing support for improvement plans and criticising the teachers’ “disruptive” industrial action.

The UST’s chair, Peter Heathcote, said the trust was committed to helping the school make the necessary improvements. “Pupil outcomes are currently far below expectations and the school has been failing its children for a number of years … We are confident that we can transform the school into a safer, happier and much more purposeful place in which all young people will be able to learn and excel.”

Official government figures published earlier this week showed the number of academies grew by a fifth between July 2016 and July 2017. The NEU says, however, that John Roan Resists is one of a growing number of campaigns bringing together parents and teachers to prevent their school being forcibly turned into an academy or being re-brokered to another academy trust where the original trust has failed.

Mary Bousted, joint general secretary of the NEU, said: “The groundswell of opposition from parents and teachers across the country … is testament to the fact that the academy bubble has been popped.”

The Department for Education said: “Inadequate maintained-schools have been turned around after becoming sponsored academies, with more than half a million children studying in sponsored primary and secondary academies that are now rated good or outstanding, and typically replaced underperforming schools.

“Converting to become an academy is a positive choice made by hundreds of schools every year to give great leaders the freedom to focus on what is best for pupils.”