An "age-appropriate" health and physical education curriculum will be ready by the start of classes next fall, based in part on consultations done after the last one was withdrawn, added Sandals.
"In our increasingly interconnected world, students often get information from unreliable and inaccurate sources," she said.
"That is why an up-to-date, relevant and appropriate health and physical education curriculum is needed now more than ever, and is why we are committed to having one in place for the 2015 school year."
The re-introduced sex ed curriculum will teach kids about homosexuality and same-sex marriages in Grade 3, encourage discussions about puberty, including masturbation, in Grade 6, and talk about preventing sexually-transmitted diseases in Grade 7, which could include information on oral and anal sex.
Christian evangelist Charles McVety and other religious leaders condemned the Liberals for going too far with the proposed changes four years ago, forcing the government to back down until now.
The government said studies show that girls as young as seven and eight years old are entering puberty, significantly earlier than in previous generations, and they need information at the appropriate time to deal with the changes.
"We've actually got a whole group of primarily little girls, but little boys too, whose bodies are way ahead of their heads," Sandals said in an interview. "That's not a political attitude survey. It's not a religous survey. That's just the way it is."
The last time the sex ed curriculum was updated was in 1998, before the widespread use of social media and smartphones, added Sandals.
"When we were doing the (curriculum) work in 2008 and 2009, even though we were thinking about Internet safety, I don't think the word sexting had even been invented," she said. "We've asked experts in various areas to have a look at the 2010 version of the curriculum to see if there areas that need to be updated."
Research shows that between 15 and 28 per cent of teenagers have sent a "sext" — a sexually explicit image or text message, and parents know teens spend a lot of time online and on their smartphones.
"Youth today need knowledge and skills to respond to these realities ... associated with the rapidly changing, technology-driven world, while also managing the risks and challenges of cyber-bullying, sexting, the prevalence of online pornography and other such issues," reads a parents' section on the Education Ministry website.
The New Democrats urged the Liberals not to back down a second time if they get attacked again by religious leaders for updating the curriculum.
"For years, the Liberals have been talking about updating the sex ed curriculum, but got cold feet and left our students using outdated materials," said NDP education critic Peter Tabuns.
One parent from every elementary school in Ontario, about 4,000 in all, will be able to provide feedback to the government through a secure survey about when certain sex information should be taught in schools.
The government said the advice from parents will be considered along with research from earlier consultations and focus groups with students, teachers and others as it finalizes the new sex ed curriculum.
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