1.
A girl began to cry once and told the the whole class that she was a hermaphrodite. After calming her down and explaining it all she agreed to answer more questions for those curious. Turns out she was just talking about her clitoris and thought it was a penis.
3.
Conservative Christian college girl is never taught how reproduction works, believes sweaty hand holding leads to babies. I give her the birds-and-the-bees talk, her parents complain to the college.
5.
My sex ed teacher in high school told us stories about a female student she had a long time ago. The student got pregnant and was freaking out to our teacher not knowing what happened because she had apparently been taking birth control. My teacher was asking her typical questions about her situation, how long she was taking them, etc. then later the girl mentions she had been taking her birth control pills vaginally. She figured that since the baby comes from there, that's where you take the pill.
7.
One girl honestly believed that she couldn't get pregnant if she didn't have an orgasm.
9.
The teen (looking kind of embarrassed), asked me "how many holes do we have down there?" I answered "women have three." Just then, the teen looks at her mom and exclaims, "See mom, I told you!!" And the mom looks confused and asks, "are you sure it's three?" I tell her, "yes, women have three - vagina, urethra, anus - and men have two." The mother goes, "men have two??" I was shocked...Long story short, I had to draw them a picture of female and male anatomy to drive the point home. They thought that women urinate from their vaginas :/ I can see how the teen could be confused, but the mom was too!
11.
I used to go to a really religious school. The girls there believed that no one actually enjoys sex, it's just the media telling you you do.
13.
My roommate freshman year of college had no idea that women could orgasm (it wasn't a religious university, but the girl had had an exclusively religious education prior). This came out during a discussion about a 'screamer' down the hall, when my roommate genuinely had no idea why a woman would be enjoying sex.
15.
A girl in her 20s honestly believed that males have an extra bone in their penis. She tried to defend herself by claiming that if a penis didn't have a bone why would it be called a "boner" when the guy was aroused.
17.
NB - Some anecdotes here are reported secondhand, or edited for clarity. More anecdotes here.