Teaching: oh god why would you ever put Greed in charge of teaching anything to anyone?

Regularly taking: He is most certainly not taking classes, that would be too much like joining things run by other people! But...

Sometimes taking: ...he does stop by the Kid's thing occasionally, just because he has some cool toys. And Al's. It would take some coaxing (and appealing to his ego) to get him to do more than watch, but he does show up.