Thousands of school children barely old enough to pronounce — let alone understand — words such as "masturbation" and "anal sex" ditched classes and took to the streets on Monday in Ontario to protest new changes to the provincial sex ed curriculum, which they say goes against their beliefs.

It was a successful first day for the "one week no school" strike organized by a group on Facebook that's calling on parents across Canada's most populous province to pull their children and teens out of class everyday this week.

One Toronto school reported that 90 percent of its 1,350 students didn't show up for school on Monday. And a representative for the city's public school board told VICE News in an email that the absence rate for its entire elementary student population increased by 144 percent compared to last Monday; 14,191 students were marked absent on April 27th at the Toronto District School Board, compared to 34,762 on May 4th. Meanwhile, one Muslim community estimated that close to 10,000 members won't go to their regular schools at all this week.

Ontario's sex ed curriculum, which was last updated in 1998, was the oldest curriculum in Canada, until the province's education minister introduced its updated version in February. Since then, angry parents and community groups have fought against it, with many critics calling it "age inappropriate", and others going so far as to call it a form of child abuse.

Changes to the curriculum include teaching students about sexual consent in grade 2, gender identity in grade 3, masturbation in grade 6, and anal and oral sex in grades 7 and 8, in the context of choosing abstinence in order to avoid sexually transmitted infections. And because it now includes topics on sexting and cyberbullying, experts are calling it the most progressive sex ed curriculum in Canada.

Sex education offered at schools in the US varies greatly according to state, with only 22 and the District of Columbia requiring such instruction in public schools. Many, like Texas and California, emphasize a curriculum rooted in abstinence. And most states allow parents to have input in their child's sex ed, or to opt-out of it entirely.

Melanie Marcus, one of the strike's organizers, pulled her daughter out of school to join hundreds of other families on Monday for a protest in front of Queen's Park, the province's legislative building in Toronto, where they plan to congregate daily for the remainder of the week. She told VICE News that while she doesn't have a problem with children learning about the science behind puberty and reproduction, she does have a problem with "the discussions of the pleasures that go with it."

"When teen smoking is on the rise, we teach them about cancer — and we put laws in place so that they can't buy cigarettes — but when teen sex is on the rise, we teach them how to enjoy it, and that doesn't make sense," she said.

Marcus and her daughter joined in as other parents and children sang the national anthem and chanted "let us be kids" and "respect my parents!" in front of the legislature.

One girl wearing orange cat ears stood for hours with a sign that read: "I'm only 6 I like ponies, I like clay Why Do you want to take my Innocence Away?"

Kimberly Cormier, another mother at the protest, told VICE News it's the parts of the curriculum that discuss gender identity and LGBTQ issues that trouble her most. "We don't need to tell the kids about transsexual, two-spirited-ness. Actually, I don't want to use this terminology because the kids are present here today. And that's exactly what we're trying to protect them from," she said.

But for transgender activist Sophia Banks, who attended school in the Toronto-area in the 1990s, learning about gender identity in grade school could have helped her understand why she wanted to try on her mother's clothes at age 11. "It would have made a world of difference for me. I thought something was wrong with me," she told VICE News. "For kids, it's not knowing about all the possibilities around gender that causes mental anguish and confusion." Banks would like to see kids in Ontario learn about sexual and gender even earlier than grade three.

Leaders of the Ahmadiyya Muslim Community in Ontario, meanwhile, are urging parents to opt out of the new curriculum if it doesn't change, come the fall. This week, they will show their displeasure with certain parts of the curriculum, including topics on gender identity and learning about intercourse, by sending youngsters to mosques and community centers for schooling.

"We feel that the government has not been very inclusive when it comes to talking to us," Imam Farhan Iqbil told VICE News in front of a group of students during class at the Baitul Islam Mosque in Maple, Ont. "I'm not saying sex ed should never be taught, but we feel there are topics that are being taught too early, and that's against our religion."

The office of Kathleen Wynne, Ontario's premier, did not respond to VICE News' request for comment. Wynne told reporters last week that despite the opposition to the curriculum, her government will not withdraw it. "I think in some case we are going to have to agree to disagree," she said.