Sex education is returning to New York City schools for the first time in nearly two decades.
Middle and high school students will be required to take sex-education classes beginning this year.
The curriculum includes lessons on how to use a condom and the appropriate age for sexual activity.
"We want to help kids to delay the onset of sexual activity, and if they choose to engage in sexual activity, to do it in a healthy way," said Deputy Mayor Linda Gibbs. "In a healthy relationship way and a healthy physical way."
The new mandate calls for students to take one semester of sex education in 6th or 7th grade, and again in 9th or 10th grade.
Children as young as 11 will participate in discussions on topics like pregnancy and the risks of unprotected sex.
"It's a good first step," said Joan Malin of Planned Parenthood. "We would like to see it in every grade every year. As kids get older, their questions would be different. The information you would want to provide would be different."
"A lot of parents don't feel equipped to deal with this issue," Malin added.
But one Flushing, Queens, parent told NBC New York sex education should be taught at home. "I have a hard time thinking of the government interfering in personal lives," said John Trevellini.
The Archdiocese of New York said the mandate on sex education was "troubling," and reinforced its stance on abstinence as "the only sure way to avoid pregnancy and disease."
"The city would be better advised to puts its efforts into promoting what truly works rather than continuing to promote a failed experiment," said the archdiocese.
Parents will be able to have their children opt out of the lessons on birth-control methods, the city said.
The classes will be coeducational. They can be incorporated into existing health education courses.