Late reply but what? If you're 18 you're legally considered an adult. If, say, you're a senior and you're having sex with a girl who is a sophmore, you can get in just as much trouble as anyone else above 18. I've seen it happen to guys when I was in high school. I will so though that a lot of times people may not really think they should be labeled as a pedophile at that age. Then again, there were some fuckin weirdos who were 18 trying to get with girls who were still in middle school that were like half their size. Again late reply, but most jurisdictions have 'Romeo and Juliet' laws in place, which are made to protect (to some extent) consenting people in the same age range.
For example in my state, sexual pictures of a minor are illegal, however, so long as the two are withing 3 years of each other, and the younger party is above 14 years old, it isn't inherently illegal edit: to have sex, etc. Divinity original sin vs 2. (pictures are always illegal)While I still do think there might be some gray areas with this, it protects younger people that are still dating within their age group from sexual charges, especially in cases where one is a minor and the other isn't.