Roughly three out of every four millennials report that they had some exposure to sex education in middle or high school, according to a new poll, and the same proportion say  they favor teaching sex ed in public schools.

Almost all of those who had sex ed classes said the information they were given was either “very” or “somewhat” medically accurate. But far fewer said their sex ed experiences were useful in real life: 37 percent said their education was “not helpful” in navigating decisions about sex and relationships.

Perhaps that’s because sex education often doesn’t cover the universe of topics and questions that young people might confront in the course of their lives.

The great majority of poll respondents said they learned about topics such as sexually transmitted diseases, pregnancy, birth control and abstinence. But only 45 percent said they discussed healthy relationships, and only 12 percent said they discussed same-sex relationships.

“It’s no wonder so many millennials didn’t find their sex education that helpful,” said Debra Hauser, president of Advocates for Youth, a nonprofit that pushes for comprehensive sex education.

“Many were in school during a time when schools taught only abstinence. Others may have received clinical information about disease or pregnancy prevention, but few were provided the information young people truly need to traverse puberty, understand the difference between healthy and unhealthy relationships, develop a positive body image, make informed decisions, communicate effectively or navigate the health care system.”

Adam Tenner, executive director of Metro TeenAIDS, a D.C. community health organization, said many cases schools are starting sex ed too late, after many students have already become sexually active.

“We’re barely getting the basic information out to kids. We’re not getting to the advanced, secondary conversations around dating and relationships,” Tenner said. “I probably know as many adults as teens who say that they’d love to have more information about what it means to date, what is a healthy relationship, how do I know if I’m in one — these are big questions that even adults struggle with.”

Establishing consent in a sexual encounter is among the topics that sex ed classes often don’t get to, Tenner said. A startling number of poll respondents said that sexual assault — which has gained attention as a problem on college campuses — is a common problem in middle and high schools.

More than half of millennials — 53 percent — said that incidents of sexual assault are somewhat or very common in high schools. A smaller but still significant portion — 29 percent — said sexual assault was similarly prevalent in middle schools.

Black women were the most likely group to see sexual assault as a common problem in K-12 schools. Half of black women saw sexual assault as a common problem in middle school, and 70 percent saw it as a common problem in high school.

The poll surveyed 2,314 adults between the ages of 18 and 35 in February. Interviews were conducted online in both English and Spanish. The poll was funded by the Ford Foundation.