A group of Ontario parents is planning to pull their children from classes Monday to protest against changes to the province’s sex-ed curriculum.

The Toronto District School Board says schools in the area have received notification from parents who say they intend to keep their children home this week as part of a “strike” against curriculum changes.

A Facebook group promoting the strike has more than 8,850 "likes," and provides a pre-written letter for parents to give to schools to explain why their kids are missing.

"We believe that the new Health and Physical Education curriculum contains information that we consider age-inappropriate and do not align with the principles and beliefs of our family," the letter reads.

TDSB spokesperson Shari Schwartz-Maltz said that, in her seven years with the school board, she has never before seen parental opposition like this.

"In some cases, some schools have received many (letters). In other cases, schools have just received verbal messages to a teacher or to the principal," she said.

Schwartz-Maltz said the mixed forms of communication have made it impossible to track exactly how many students will be missing classes, but that schools will be running regularly this week despite any absences. Students participating in the strike will be expected to make up missed work, just as they would if they missed class because they were sick.

Rida Hasan, whose son is in Grade 3 at McBride Avenue Public School in Mississauga, Ont., said she has heard from parents planning to keep as many as 150 students away from her son’s school.

"I want to send the schools and the ministry a message that if they do not listen to our concerns, we will pull our kids out of school for good," Hasan said in a phone interview.

Like other parents, Hasan said she is uncomfortable with changes to the sex education curriculum that would teach Grade 1 students the correct terms for genitalia, explain puberty in fourth grade, and discuss forms of sex and sexually-transmitted diseases in Grade 7.

The government has said the updated curriculum will teach children about consent and safe and responsible relationships, helping kids to navigate a world in which sexual images and often inaccurate information is already readily available online.

But some parents fear the curriculum will expose students to too much, too early.

"I think that (Premier) Kathleen Wynne is using the children for her own sexual revolution," Hasan said.

In particular, she said she is concerned about how early the curriculum would introduce ideas about sexual orientation and gender fluidity.

Schwartz-Maltz said that teachers and principals have been doing their best to answer questions and discuss with parents about the curriculum changes, but Hasan said she feels ignored by the Ministry of Education, which actually designed the teaching material.

"I want to get the message out for people to join the strike because we want to be heard," she said.

As for her eight-year-old son, who will be missing a week of third grade, Hasan said he understands the issue and is supportive of her decision.

"Right now, he’s just happy that he’s getting a week off," she said.