Absolutely 16, 17 and 18 is mature. Not every single girl obviously but the majority - yes. This isn't scary Oldspice. Schoolgirls are wonderful. I wouldn't attempt to make a pass at one but I certainly know a lot of them like the admiring glances. To a certain extent you and I stand on two sides of an ethical grey area. We would both agree 13 is too young and 21 is OK. But that area in the middle is open to debate.