Those opposed to Ontario's updated sexual education curriculum gathered in London's Victoria Park on Tuesday.
About 500 protesters chanted phrases like "Our children, our choice," as they then marched through London's downtown core.
Opponents of the province's proposed curriculum say teaching children about sex should be left to parents, and that it's too much, too soon.
Protestor Nikee Steinhoff says, "Our advice to Premier [Kathleen] Wynne is simply this, we want you to resign...It's putting the power of suggestion into their minds to start experimenting early."
But at least one person at the protest was arguing the opposite, saying the protestors are misguided.
Psychologist Dr. Guy Grenier says not having sex education is a greater threat to the province's children.
"It puts them at risk for STIs, it puts them at risk for earlier teenage pregnancies, it puts them at risk for sexual assault. It's through knowledge that we empower our children."
The march echoed a larger protest at Queen's Park, where thousands gathered with signs calling the curriculum irresponsible and complaining there wasn't enough consultation with parents.
This is Ontario's second attempt to revise the sex ed curriculum, which was last updated in 1998, before the spread of smartphones and sexting.
Changes include teaching Grade 3 students about same-sex relationships, Grades 4 and up learning more about the dangers of online bullying and teaching the dangers of sexting in Grade 7.
Lessons about puberty would move from Grade 5 to Grade 4, while masturbation and "gender expression" would be mentioned in Grade 6.
Education Minister Liz Sandals says those on the Conservative right have politicized the issue.
"I'm telling you, this has changed from being simply, genuinely concerned parents into something that is identified in the correspondence that I am receiving as the Liberal curriculum vs. Conservative thought."
With files from The Canadian Press
