Seven primary schools in New South Wales are offering to participate in the pilot of an ethics course as an alternative to religion classes.

The Education Act prohibits non-scripture students being taught while others receive religious instruction.

It reflects a 19th Century deal between the New South Wales government and churches.

Scripture opt-out rates can be as high as 50 or 80 per cent.

P and C Associations, church groups and the Saint James Ethics Centre say that makes it a social justice issue for students.

The President of the Federation of NSW P and C's, Dianne Giblin, says students who opt out of scripture are being discriminated against.

"All the other young children are allowed to go off to their various faiths and look at their own ethics and their own values and morals, and the rest of the school are not allowed to do anything else," she said.

"And this is important for these young people who are missing out on the opportunity to have a look at their ethics and their values."

They have asked Education Minister Verity Firth to approve a pilot course on ethics, values and general religion.

Bungendore, Hurstville and Neutral Bay primary schools are among those offering to run the course.