Nearly 1,800 health care professionals have signed a petition calling on Ontario Premier Doug Ford to stop his plan to revert to an old sex-education curriculum.

The petition was delivered to the Ontario government on Tuesday. It says the 1998 version of the health and physical education curriculum, slated to be taught in schools starting in September, could jeopardize the health and well-being of Ontario's children because it is incomplete and out-of-date.

It urges the government to reinstate the 2015 curriculum, which it says was implemented by the former Liberal government after extensive consultation with community groups.

According to the Ontario education ministry, the old version of the curriculum will replace the revised version in four weeks.

Ontario NDP Leader Andrea Horwath said the rollback is the "wrong thing to do" and it shows that Ford has "mixed up" priorities.

NDP Leader Andrea Horwath, surrounded by health care professionals, speaks at Queen's Park on Tuesday. (CBC) ​ ​

Horwath joined a handful of health care experts at Queen's Park on Tuesday to slam what she says is a move to turn back the clock. The professionals who signed the petition include family doctors, pediatricians, nurses, midwives and social workers. It was endorsed by 19 organizations.

"If we don't teach children up-to-date sex ed curriculum, a complete up-to-date sex-ed curriculum, we are putting our children's health at risk," Horwath told reporters. "We have a responsibility to teach kids about healthy relationships, about consent."

Horwath said the curriculum to be taught in September was written before the advent of Google, social media, texting and legal same sex marriages in Ontario. It does not include information about such topics as sexual orientation and gender identity, she said.

She said, for example, children need to know how to protect themselves from bullying, cyber bullying, abuse and sexually transmitted infections, and the old curriculum fails to address those issues in a meaningful way.

In a statement before the news conference, Horwath said: "Doug Ford's plan to plow ahead with a sex-ed curriculum that was written before Google existed not only shortchanges students — it puts their health at risk. Let's not allow our children's health, including their safety and mental health, to be put at risk because of Ford's politics."

According to the Ontario education ministry, a 1998 version of the curriculum will replace a revised version that was implemented by the former Liberal government. (Shutterstock/Syda Productions)

Dr. Andrea Chittle, a family physician in Guelph, told reporters at the news conference that children and youth in Ontario need comprehensive education about sexual and reproductive health in order to make informed decisions about their personal lives.

Chittle said the old curriculum has "really important gaps and omissions" and lacks information about such groups of people as the LGBT community, disabled people and Indigenous people. She said the old curriculum was updated in part because members of the LGBT community were being bullied and harassed and their exclusion from the curriculum was seen a contributing factor.

"Reverting back to the 1998 curriculum is an affront to the youth of Ontario," Chittle said.

"It is imperative that children learn about difference and inclusivity, consent and safety. The human development and sexual health components of the 2015 curriculum are critically important for informed decision-making related to health behaviours and relationships," she said.

"Ontario's children deserve a current, complete and evidence-based curriculum."

Dr. Andrea Chittle, right, a family physician in Guelph, says: 'Reverting back to the 1998 curriculum is an affront to the youth of Ontario.' (CBC)

According to the Canadian Paediatric Society, the old version of the curriculum is a "potential source of harm" for Ontario's children because it raises the risk of misinformation, discrimination, disease and abuse.

"As a family physician, and a mom, I think we have a critical responsibility to do better for our kids," Chittle said.

26 school boards speak out on issue

Meanwhile, 26 school boards in Ontario have expressed concerns about the province's plan to revert to the old curriculum and they are asking for clarification on what should be taught in the classroom weeks from now.

The list includes public school boards in Toronto, Peel, York and Halton Regions, Hamilton-Wentworth and Ottawa-Carleton Districts.

"There are still a lot of questions out there," Horwath said. "I think it's going to be chaos in schools come September."

One board, Rainbow District School Board in northern Ontario, has said it will not teach the old curriculum.

The boards say teachers, parents, staff and students are confused about what will be taught in the classroom.

To add to the confusion, the website of Ontario's education ministry contains the revised curriculum from 2015, not the version from 1998.

Consultation with parents to begin next month

The Registered Nurses Association of Ontario, the Society of Obstetricians and Gynaecologists, the Nurse Practitioners' Association of Ontario, the Association of Ontario Midwives, Canadian Women in Medicine, the Ontario Association of Social Workers, the Ontario Medical Students Association, and Planned Parenthood all have signed the petition.

Health Minister Christine Elliott said Tuesday that she welcomes the feedback from health professionals, but wants to hear from parents. She said consultation with parents will begin in September.

"Parents know what's best for their children. Parents know at what age it's best for children to learn about certain things," she said during Question Period in the Ontario legislature.