Independent Sydney MP Alex Greenwich is going up against religious schools in his aim to protect the rights of gay students. He is preparing a bill that would ban schools from expelling students on the grounds of their sexuality, which is strongly opposed by most faith-based educational institutions.

Getting expelled from or getting denied admission to a school because of one's sexuality is already deemed unlawful under the NSW Anti-Discrimination Act. However, there's a caveat to this law. None of these protections can be applied "in respect of a private educational authority," which means private religious schools can discriminate LGBTI (lesbians, gay, bisexual, transgender, and intersexed) students.

The young MP is seeking to delete this caveat.

"Currently in NSW students can cruelly be expelled for being gay. This is wrong, and my bill will end this," Mr Greenwich said in a statement to GSN.

"The threat of expulsion for being who you are has a hugely negative impact on vulnerable LGBTI high school students. This is a major issue for the inner city. High school spots are already extremely limited and the growing numbers of LGBTI families in Sydney don't need further restrictions placed on their schooling options."

He added that Sydney has the highest number of same-sex couples in the country and a thriving LGBTI community. However, LGBTI youth have no public high school to go to where they are safe from the risk of being expelled.

But many religious schools are opposing the move, telling The Sun-Herald that it is important to retain the exemption to preserve their religious freedom.

"It speaks for itself," NSW Catholic Education Commission acting executive director Ian Baker said. "It's exercised with great caution and consideration. The objective is not to punish, but to protect the rights of those families who send their child to a school based on a religious faith.

"We couldn't agree to the exemptions being removed unless we could be assured that there's an alternative way of guaranteeing freedom of religion, which is an internationally recognised human right."

"Most private schools have a religious ethos, they stand for something, and if these exemptions were removed that would break down the ability of these schools to maintain whatever their particular ethos is," Laurie Scandrett, chief executive of the Sydney Anglican Schools Corporation, added.

The Australian Council of Jewish Schools is not opposed to the planned bill, though.

"While Jewish schools jealously guard against any incursion into our ability to teach the Jewish religion in a manner consistent with its tenets, and consider those tenets and that ability fundamental to our existence, we do not see any practical limitation, or the imposition of any practical burden on that ability from the amendments deleting the specific exclusions to the Anti-Discrimination Act," executive director Len Hain has been quoted by The Sun-Herald as saying.

Greenwich said that the loophole in the law is unique in New South Wales. He will be introducing the bill in August as parliament resumes, hoping that it will go to a vote by the end of the year.