And in 2015, a Christian school in Mandurah told the father of a seven-year-old girl his daughter could only stay at the school if she didn't tell anyone he was gay.
Greens spokeswoman for sexuality and gender diversity Alison Xamon said the law needed changing to bring it into line with community expectations.
"So it means that if an employee is LGBTIQ, or if a woman becomes pregnant and becomes a sole parent, if someone is divorced, then those sorts of reasons no longer become a lawful excuse to sack someone or to kick a child out of school or to deny enrolment to a child," she said.
"And the reason for that is because fundamentally at the end of the day we need to remember that schools are there to also provide a service.
"They are receiving taxpayer dollars and frankly what someone's sexuality or gender identity or marital status is, is really irrelevant to being able to teach or to garden or to be able to work in administration at a particular school."
The legislation introduced by Ms Xamon will allow schools to still discriminate against someone on the basis of their religious affiliation.
"The reason I decided to keep that in there is because what I'm not trying to do is mess with the fundamental integrity of the make-up of religious schools," she said.
"We did actually just pass marriage equality laws and I think the majority of Australians would think that it's appalling someone could legally get married one day and the next get sacked.
"So a Jewish school can still have Jewish students, Muslim schools can still have Muslim students, Catholic schools can still prioritise Catholic students, there's no problem with that."
LGBTI rights campaigner Brian Greig, a former WA senator, said the current law was "unfair and cruel" and had an "unhealthy, unhelpful" message for LGBTI students.
"One of the things we have to keep in mind is the impact this has on students in religious schools who are still in the closet," he said.
"In the case of Craig Campbell, for example, who was dismissed from a school in Waikiki; what message does that send to the students in the school, particularly those who might be coming to terms with their sexuality?
"It makes absolutely no sense for church schools, which most seem to say they embrace and love and nurture their LGBTI students, but at the same time persecute their LGBTI teachers."
Ms Xamon said she had not yet discussed the Greens bill with the government, who would need to lend their support for it to become law.
"I'm hoping that we're going to be able to have a discussion," she said.
"I do know that the McGowan Government to date has indicated a reticence to engage in the discussion and has wanted to defer to what's ever happening at the national level in terms of religious exemptions.
"These are discriminatory, out-dated provisions on our statutes and I am anticipating that at some point in the future, whether it be in a year or whether it be in a decade, that we are going to see a wind back of these laws at a federal level."
A spokeswoman for Attorney General John Quigley said the McGowan Government was committed to addressing discrimination against the state’s LGBTI community.
"Last year, the state government introduced the Historical Homosexual Convictions Expungement Bill 2017 (WA), demonstrating the state government's commitment to addressing issues of discrimination against the LGBTIQ community and ensuring fairness and equality for all Western Australians," she said.
"The Premier also offered an apology on behalf of the State Parliament to those impacted by the old laws.
"The state government is currently awaiting the outcomes of the Commonwealth Review into Religious Freedoms, chaired by the Hon Phillip Ruddock, as the provisions in state legislation mirror those of the Commonwealth.
"In respect of the Bill as moved by the Hon Xamon today the State Government will consider the legislation and provide its response in due course."