[m_myers]

Which is pretty justified, in my experience. There's a reason 13-year-olds are called "minors"; most of them are not yet mature enough to make good decisions on their own, so guidance is necessary.

Of course there are exceptions to the rule, but the mother certainly knows her child better than you or I do.

[jdechko]

Oddly enough, or not, 13 is also around the time where kids start puberty. It's not just a physical change, but also a time where kids are most impressionable. The "kids toys" get put away and they stop behaving like a child, because they are old enough to understand certain things. In short, they are becoming little adults.