The first lesson was about Pyrote, a boy who I knew in Thailand. He died of AIDS. When it came time for them to ask me questions, the first girl asked, "How can we help children like Pyrote?" Ding, Ding, Ding. I was so happy that was the reaction. The second question was, "How do people get HIV and AIDS?" I thought, "Wow, how can she not know that?" I did the same lesson with 8 classes and around half of the students had the same question.
I was told kids are taught about HIV/AIDS, but if they were taught, they have forgotten. Not sure how everyone would have reacted if I said sex, so I just avoided it by exchanging the words "have a relationship with out a condom" for "have sex without a condom". The kids listened, nobody laughed...pretty good.
You might think with the AIDS epidemic it is crazy for kids not to know. The thing is while the US with 1.2 million HIV+ people has an epidemic, according to the CIA Factbook, Korea has 12,000. The kids ought to know, but not knowing is a lot less dangerous than it would be in most other countries.