Yikes, Little Dude

So my son has somehow gone from the passive, shy little sweet angel to the kid who pulls hair.  I think it's that he changed day care providers this week.  His former provider, who he'd been seeing for over a year and a half, had an older boy who was the dominant one of the bunch.  His new day care provider has a child who is just as passive as my little guy WAS.  I think that little guy has decided that he needs to be the boss.  But I wish he wasn't such a jerk about it.  Hair pulling?  Pinching?  Dude, seriously.