A gay author whose visit to a Catholic secondary school was cancelled has praised striking teachers for “standing up for LGBT students”.

Simon James Green urged people to support the staff who are protesting.

He had been invited to the John Fisher School in Croydon, south London, as part of World Book Day in March to talk about his novel Noah Can’t Even, which features a gay character.

Southwark Archdiocese, which oversees the school, said it had recommended that school leaders cancel the visit because “from time to time materials and events emerge for consideration that fall outside the scope of what is permissible in a Catholic school”.

The diocese also intervened to remove several governors supporting the school’s leadership team, who wanted the visit to go ahead.

The National Education Union (NEU) has said a settlement to the dispute would be expected to include the reinstatement of the governors and of the author’s visit.

Further strike action is planned for next week if agreement is not reached before then, the union added.

On Thursday, striking staff were commended by Mr Green, an author of young adult fiction.

He tweeted: “Today @NEUnion members from John Fisher school are striking over my banned school visit and their sacked governors.

“They’re standing up for LGBT students everywhere who need to see the reality of their lives in books. Please show them how much support they have.”

People identifying themselves as parents of pupils who attend the school voiced their support in response to the tweet.

One tweeted: “I fully support the Teachers & the Leadership at the school. The Diocese & Director of Education of the Diocese need to be held accountable for their Draconian views & actions.”

Another wrote: “I’m very proud of the school, its teachers and leadership for making such a strong stand against the diocese’s actions.”

An Ofsted monitoring report said the decision to cancel the author’s visit had “unnerved and upset many in the school community”.

The report also said the archdiocese’s decision to impose an interim executive board (IEB) after suspending the governing body – which voted to back the school leaders’ decision not to cancel the visit – was “made unilaterally and without due regard to the published statutory guidance”.

An NEU spokesperson said: “Acas talks are ongoing, and the NEU remains open to continuing discussions to reach a settlement to this dispute that would see the reinstatement of the former foundation governors and the reinstatement of the visit to the school by the author Simon James Green.

“Those are the expectations of our members. The next day of planned strike action is for 4 May should no agreement have been reached.”

Rob Kelsall, national secretary of the NAHT school leaders’ union, wrote to the Archbishop of Southwark on Thursday to express concern over the “disturbing developments” at the school.

He said it was to the “immense credit” of pupils and staff that the Ofsted monitoring report had found that the personal development of pupils was “well led” and that the regulator had described the school as a “caring community”.

He added that Ofsted’s finding that the archdiocese’s decision to impose an IEB was made without regard to statutory guidance was “disturbing”.

“Since the formal inspection by Ofsted, and the subsequent appointment of foundation governors by the archdiocese, the stability of governance has continued to deteriorate, specifically as a direct result of some of the foundation governors’ actions,” he wrote.

“Yesterday, I visited the school and have seen first-hand disturbing evidence of continued efforts by some foundation governors to undermine the governance and leadership of the school.”

He added that members had reported “misogyny, intimidation and threats” by new governors, with “unreasonable demands” made on existing governors and staff, which was having a “serious impact” on their wellbeing.