The Presbyterian minister who led an attack on the screening of a film about children with gay parents at a Sydney high school had his scripture classes at the school dramatically slashed last year, documents seen by Fairfax Media have revealed.

Gayby Baby was due to be shown at Burwood Girls High and up to 20 other schools in NSW on Friday before an extraordinary ministerial decree from NSW Education MInister Adrian Piccoli led to a statewide ban on the documentary during school hours.

Minutes from a meeting at the inner-west high school show that the leading force behind the campaign to stop the film, Mark Powell, had the special religious education (SRE) classes he oversaw cut from once a week to once a term after a school council found they were incompatible with the school community.

Reverend Powell was the chairman of GeneR8 ministries who administered the classes at the school.

Quoted throughout last week's coverage as a spokesman for outraged parents who "runs a local youth group", the online activity of the father-of-six revealed a man personally involved in drumming up support for the ban on the film.

"Just heard today that Burwood Girls is making it compulsory for all students to attend the screening of a film promoting homosexuality," he wrote. "All this from the same principal who banned SRE from continuing to be taught in the school a couple of years ago."

Within minutes Mr Powell's supporters had formulated plans to ensure that the film was banned, including how to get the Islamic community and media involved.

Mr Powell denied the actions were motivated by malice towards Burwood Girls High principal Mia Kumar, but acknowledged that he was "disappointed" after a school council meeting in November 2013 concluded that timetabled SRE classes should not continue.

"I'm a pastor not a politician," Mr Powell told Fairfax Media. "This was about combating coercion, I would also have a real problem with forcing everyone to watch a film about the Ten Commandments and making everyone dress up as Moses."

No formal complaints from parents about the film have been received by the school.

Minutes seen by Fairfax Media reveal that the school decided to discontinue classes after a letter from Mr Powell's Gener8 ministries was "not received well" by the school council.

"Burwood Girls High School was a test case, and was not successful in the implementation model," the school council found.

A spokewoman for Burwood Girls High School referred Fairfax Media to the Department of Education for comment. The department did not respond to a request for comment before deadline.

A job ad from the previous year reveals that up until that point Gener8's missionary work in the school had been expanding, a part-time officer reporting directly to Mr Powell was hired and SRE classes had been timetabled into class time.

At the same time, Mr Powell, a 43-year-old former Catholic, was about to become one of the youngest moderators in the history of the NSW Presbyterian Church while he juggled the demands being a chairman and SRE co-ordinator.

In June Mr Powell described schools as a "a very strategic place to minister," in the Presbyterian Pulse magazine.