Teachers need to limit websites at school because students are
in school to learn. If they did not limit certain sites, children
would be on those sites instead of learning what teachers are
trying to teach them.
Technically, there is no actual age limit. While the majority of
college students will be fresh from high school or at least in
their early 20s, it isn't too uncommon to see people in their
30s-50s coming back to school.