Proposed changes to the Anti-Discrimination Act could allow religious-based schools to give admission preference to students who share their religious beliefs.

Education Minister Jeremy Rockliff told Parliament yesterday that the changes would allow religious schools to operate for the benefit of people who shared their faith.

"We want to support faith-based schools providing faith-based education services primarily to the families of congregations and religious communities," he said.

"This does not mean that they can discriminate on any other grounds - only religious beliefs."

But opponents of the changes fear gay or transgender students and parents could also be refused enrolments if the government's proposed law is passed.

Anti-discrimination commissioner Robin Banks is among those against the amendments, saying schools may already seek permission to preference a child of its religion if there was competition for limited places.

Tasmanian of the Year Rodney Croome has warned the bill may violate the state's constitution.

Mr Croome has argued parents should have the right to choose where to send their children to school, and all students ought to have the right to feel welcome wherever they enrol.

Greens justice spokesman Nick McKim told Parliament the bill would pave the way for people to act like bigots, and shift the onus of proving unfair discrimination away from schools and onto students.

Mr McKim argued the bill would not protect the religious freedoms of parents or their children, but instead provide cover for priests, pastors and religious principals to discriminate.

"You're giving all the power to schools and you're saying to parents, 'if you don't like it, take us to court'."

But Mr Rockliff said the changes would bring Tasmania in line with other states and territories.

The laws will soon be debated in the upper house.