Um...really? First of all, nowhere does it say he's in high school. Even if we assume he lives at home (which is implied but not guaranteed), he could be in college. Almost all college students live at home when they aren't at school. He could be 22, for all you know. Second, even if he is in high school, he could easily be 18, which would make him legally an adult, not a child. Third, the average age when people start having sex is about 17, so essentially, over half of people have sex in high school (mathematically that's an awkward conclusion, but going off the statistics themselves, it's true; I believe it's something like 60%). That's a lot of opportunity for you to be grossed out. Finally, the age of consent in most states is 16, some places lower (or lower in certain circumstances). If the law is perfectly okay with it, why should you care?