Girls hitting puberty earlier? Is milk to blame?

It's when you finish highschool and are capable of working and feed yourself, which implies your ability to support a baby, should one come into the picture.

That makes sense.

Boys would be complete perverts anyway, with or without balls and/or puberty. Why care?

Again, is puberty solely a physical thing or does it also trigger brain development? Earlier puberty without earlier/faster brain development for either gender could cause problems, but if brain development goes hand in hand with puberty, then there will be some serious problems with girls starting 4-5 years before boys.

All I remember from those classes is "hair and other stuff will start to grow, BUT DO NOT PANIC". More or less.