A school in which disgruntled staff staged a series of strikes has been put in special measures after Ofsted claimed that “untenable tension” within the school community was adversely impacting pupils’ education.

Last year staff at Hasland Hall Community School, in Chesterfield, held three strikes to protest against unruly pupils and excessive workloads.

And while the NASUWT-organised strike action was suspended in November, an Ofsted inspection the previous month found “untenable tension across the school which is having an adverse effect on the quality of education, behaviour and school improvement”.

The inspector advised the school is ‘inadequate’ because it is “failing to give its pupils an acceptable standard of education”.

The report also states the quality of education provided is “not good enough” and senior leaders have “not ensured that curriculum plans are aspirational”.

Almost one-third of parents said their children were not safe in school and pupils are not confident staff can deal with bullying concerns – while some staff said “they did not feel safe themselves”.

This poor behaviour is said to be “affecting pupils learning and achievement” and the inspector said leaders must work to establish “an ethos of respect and understanding”.

It’s not the first time Ofsted has taken aim at unions. An Ofsted study published earlier this year claimed the “antagonistic voice” of unions stalled improvements in “stuck schools”, with some headteachers bemoaning “strong union representation resisting action to improve the culture of the school”.

In a letter to parents, acting headteacher Steve Edmonds said the school was “deeply disappointed” with the judgment but recognised “the schools must change and improve”.

He said since the inspection an action plan has been developed to address changes in behaviour management and an audit of safeguarding procedures has been launched.

On top of this, “anti-bullying policy and procedures have been amended in order to make the reporting process more robust”.

He asked that parents give “full support to the school during a time of uncertainty and public challenge” and that they don’t take to social media to air grievances with the school.

He added: “On a daily basis the staff, senior leaders and governor continue to do their very best for your children.”

The NASUWT did not respond to a request for comment.