An interim sexual-education curriculum introduced by Ontario's Progressive Conservative government discriminates against some students and puts them at greater risk of sexual violence, the province's human rights commission said Tuesday as it joined a legal challenge of the document.

The interim curriculum, which replaces a modernized version drafted by the previous Liberal government in 2015, discriminates based on sex, sexual orientation, gender identity and gender expression, the commission said.

"The children most affected by the changes to the education curriculum are the same children who are at the highest risk of exclusion, harassment and violence," Chief Commissioner Renu Mandhane said in a statement.

"This is not the safe, welcoming education experience envisioned in the Human Rights Code. We stand with students across Ontario who are using their voice to make sure all students' human rights are respected."

Repealing the modernized curriculum was one of Premier Doug Ford's key campaign promises, and one of the first things he did after taking office this summer. (Chris Young/The Canadian Press)

Six students' families filed a complaint with the Human Rights Tribunal of Ontario in August, claiming the interim curriculum makes no mention of issues such as gender diversity or the rights of LGBTQ students.

Their lawyers argued that the government's decision to repeal the modernized curriculum violates the province's human rights code and should be declared unlawful. The lead applicant in the case is an 11-year-old transgender student.

The 2015 sex-ed curriculum included warnings about online bullying and sexting, but opponents, especially social conservatives, objected to the parts of the plan addressing same-sex marriage, gender identity and masturbation.

Repealing the modernized curriculum was one of Premier Doug Ford's key campaign promises, and one of the first things he did after taking office this summer.

Province consulting public online about curriculum

Last month, the Tories began a cross-province consultation to develop a new sex-education curriculum, promising it would be the largest in the history of Ontario.

At the same time the government introduced an interim lesson plan, which was delivered to public school boards and posted online after repeated requests from educators who sought clarity on the issue.

Critics of that document said it only makes passing mention of modern concepts such as the internet and cellphones but largely reverts to the vague language and broad topic outlines used in the old curriculum last updated in 1998.

Kayla Iafelice, spokeswoman for Education Minister Lisa Thompson, said the government is moving forward with the provincewide consultations through online submissions, and will soon roll out an online survey and telephone town halls.

"As this matter is before the court, it would be inappropriate to comment further," she said.

The Canadian Civil Liberties Association and the union representing Ontario's elementary school teachers have also launched their own legal challenges of the interim curriculum.