TORONTO -- Ontario schools will go back to teaching the same sex-ed curriculum they did in the late 1990s this fall after the province's new government announced Wednesday it was revoking an updated version brought in by the previous regime.

Just over a week into the summer break, Education Minister Lisa Thompson said ministry staff were working to inform school boards of the decision to revert to the curriculum that was in place before 2015.

The older curriculum will remain in effect until the government completes a "fulsome consultation respecting parents" on how to modernize the material, she said.

The newer sex-ed curriculum sparked controversy, particularly among social conservatives, when the Liberal government introduced it three years ago.

It was the first time the curriculum had been updated since 1998, and it included warnings about online bullying and sexting that were not in the previous version. But protesters zeroed in on discussions of same-sex marriage, gender identity and masturbation.

The updated document has its supporters, however, including tens of thousands of people who signed a petition to save it after the Tories -- who vowed to scrap it during the election campaign -- were elected last month.

A group also paid for a three-metre-long sign defending the curriculum. "Dear PC MPPs," read the sign, which was parked outside the legislature Wednesday. "Don't let the religious right hijack sex-ed."

Ontario's two largest teachers' unions said they oppose the decision, noting that parents and educators were consulted extensively before the curriculum was updated.

Sam Hammond, president of the Elementary Teachers Federation of Ontario, said the move is a "huge disservice" to students, who need to learn about critical issues such as consent.

What's more, given the amount of input teachers, experts and parents had in the update, any new consultations are likely to give a similar result, Hammond said. He encouraged parents to call on Thompson to save the updated curriculum.

The decision also doesn't leave teachers much time to alter their plans for the fall semester, said Harvey Bischof, president of the Ontario Secondary School Teachers Federation.

"Nobody wants to be unprepared, it's certainly not the best approach to classroom practice to make last-minute decisions or to have last-minute decisions foisted upon our members," he said.

"And so it doesn't feel like a thoughtful approach, it feels like a bit of a knee-jerk reaction."

Some parents, too, said they would have to make adjustments in light of the change.

Megan Houston, a mother of three -- aged two, four and 21 -- said it will affect how she talks to her younger children about sex, mental health and other subjects that were addressed in the newer curriculum.

"It makes me, as a parent, more vigilant," she said. "For my four-year-old, for example, we're talking about things like personal space."

The earlier curriculum, which was taught to her oldest daughter, glossed over some key issues, she said.

"While there were mechanics of things talked about, it was separating this idea of sex and feeling and emotion. Whereas with this new curriculum, it really ties in this idea of 'sex is not just something that your body does, it's something that will affect you emotionally,"' she said.

Others rejoiced at the news, saying parents and medical professionals should play a bigger role in creating the curriculum.

An organizer with the Thorncliffe Parents Association, a group that opposed the curriculum brought in by the Liberals, said the move was a victory for parents.

Khalid Mahmood, a father of five, said he was uncomfortable with grade school children learning about homosexuality, a topic that was covered in the updated curriculum.

Some observers raised concerns about how Wednesday's announcement would affect inclusion in schools.

"Our schools should be more understanding of all diversity, of all religions, of all sexual orientations and gender identity," said Susan Gapka, a Toronto-based transgender activist who has run for school trustee.

"To repeal this would take us back about 20 years before texting and smartphones," she said.

Lee Airton, a professor in the Faculty of Education at Queen's University, said teachers can still create an inclusive environment even with the older curriculum.

However, the change could affect how some teachers feel in the workplace, the professor said.

"I worry about new, young and precariously employed teachers who are gender and sexual minority people and whether they will experience a chilling affect in their teaching and whether they will feel less supported by their administration," they said.

--With files from Daniela Germano and Paola Loriggio