Ontario Premier Dalton McGuinty, shown earlier this year at a school in Windsor, says Catholic schools will have to teach the province's new sex education curriculum. (Canadian Press)

Premier Dalton McGuinty says Ontario's Catholic schools will have to teach a revamped sex ed curriculum that has drawn fire from conservative groups who charge it will corrupt young minds.

McGuinty says all publicly funded schools must teach the curriculum, which will see lessons taught to kids as early as Grade 1.

Starting this fall, the revised curriculum will see Ontario students learning about masturbation in Grade 6 and oral sex at age 12.

The self-described "family focused" groups are mounting a campaign to get rid of the program and calling for a rally May 10 to put pressure on the governing Liberals.

They say teaching sixth-graders about masturbation and vaginal lubrication and 12-year-olds about oral and anal sex is inappropriate and borders on criminal.

But McGuinty — whose wife is a Catholic school teacher — is standing behind the curriculum, saying it's necessary in an information age where children will learn about it anyway from their friends or the internet.