Board Thread:Off Topic/@comment-50.142.69.70-20130713234936/@comment-10390252-20130714195854

This is purely a guess but, assuming Ruby is about high school starting age, the girls' ages are probably like this:

Ruby: 13-14

Blake: 14-16

Weiss: 14-16

Yang: 16-18

That said, I wouldn't be surprised if all the girls except Yang are in Freshman year.

I think that Beacon Academy may have a policy of having Junior or Senior year students 'mentor' small teams of younger students as part of their more advanced tactical and strategic studies (learning to be a team leader, in other words). Note how the guy in the JAUN team is so much taller, and possibly older, than the others. So, Yang may (at least officially) be the leader of team RWBY.