A motion was passed on Saturday at the P&C annual general meeting to write to Education Minister Rob Stokes and urge him to change the rules that prevent students who opt out of scripture or ethics classes from doing any educational activities while SRE is being offered.

The motion said the P&C would ask Mr Stokes to amend the department's religious education implementation procedures to ensure that "all students participating in special religious education may be granted access to educational opportunities that align with the curriculum during the time scripture is being taught".

But a spokesman for Mr Stokes said the government would not be "revisiting its position".

"Any move to allow students to participate in formal classes during this time will unfairly disadvantage students who have a legal right to attend these classes," the spokesman said.

The motion came as the NSW Department of Education for the first time published 2016 and 2017 data last week showing the number of students who did not nominate a religion on their enrolment form.

The data showed the number of students who listed no religion, not stated (intentionally) or unknown/not had risen more than 6 per cent from 2016 to 2107. At the same time, total enrolments grew 1.25 per cent.

The latest data was published after the group Fairness in Religions in Schools (FIRIS) accessed earlier enrolment data under freedom-of-information laws. That data revealed more than 40 per cent of the state's 795,000 students do not list any religion on their enrolment form, which is an optional section.

If a student does not nominate a religion, the principal writes to parents informing them of the available religious programs at the school.

The NSW Teachers Federation supports SRE but at its council meeting on August 5, it decided to review its existing policy before its annual conference next year.

A spokesman for FIRIS, Darrin Morgan, said the group supported the P&C motion.

"This would be a very easy change for the minister to make because it is not in legislation, it is just in their implementation procedures," Mr Morgan said.

It is also not clear how many students who nominate a religion attend scripture because the department does not track SRE enrolments, despite a recommendation from an independent review into scripture in the state's schools.

But a spokesman for Christian SRE, Murray Norman, said 71 per cent of NSW students did SRE and it would be unfair to them if other students were allowed to do extra class work.