If you want to start a controversy in education, just say two words: sex ed.

What students learn about pregnancy prevention, sexually transmitted diseases, and human sexuality is one of the most hotly contested debates in education. The result is sex education that's patchy at best and just plain wrong at worst.

Most high schools don't teach students the 16 topics the Centers for Disease Control and Prevention recommend will set them up for healthy sexual behavior.

This has consequences: While teenagers are having a lot less sex than they were in the 1980s, teenage sexual behavior is getting riskier. Students in 2013 were less likely to say they used a condom the last time they had sex than students were in 2003.

Here's what students in every state learn about preventing pregnancy and STDs, according to a recent CDC report.

1) Students in New Jersey learn to use condoms. Not so much in Indiana.

The majority of high schools in most states included in the survey teach students about the effectiveness of condoms in preventing pregnancy and sexually transmitted diseases. But condoms are only effective if they're properly used — and when it comes to demonstrating that, some states are pretty squeamish.

The undisputed leader in condom education is New Jersey, where 93 percent of schools say they teach students to use them, as well as Washington, DC.

2) Most states don't teach students about very effective contraception

Hormonal contraception, such as the Pill, can't protect against sexually transmitted diseases. But it's pretty fantastic at preventing pregnancy. Still, students tend to learn more about condoms than these more effective methods.

(This map includes all forms of the IUD for shorthand's sake, but the copper IUD doesn't contain hormones.)

3) The one policy every state can agree on? Abstinence.

The era of abstinence-only education in the US is mostly over. But abstinence is, of course, the most effective way to not get pregnant or get an STD — and it's one that nearly all states feel comfortable emphasizing.

4) Some high school students aren't using birth control

Just because students learn about birth control doesn't mean they'll use it. More than one in 10 high school students nationally said in a 2013 survey that the last time they had sex, they didn't use any method of preventing pregnancy.

Not every state participated in the survey, but of those who participated, Texas was where teens were having the riskiest sex. Nearly one in five ninth- through 12th-graders said they didn't use protection the last time they had intercourse.

5) Where teenagers are still getting pregnant

Here's some good news: Nationwide, the proportion of teenage girls getting pregnant each year has been falling. It hit an all-time low in December. And it's falling faster for younger teens than older teens, which suggests that evidence-based sex education might be working.

The teenage pregnancy rate is declining everywhere, but it still varies a lot by state. Texas, where students report one of the highest rates of unsafe sex, perhaps unsurprisingly has one of the highest teen birth rates in the nation.

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