Parents are the best teachers, because they're a parent that knows the child better than anybody else. Also, they teach the child rules about the world and the taught how to speak. Otherwise, they'll be talking gibberish and you'll see teens crawling around.
But, parents might teach some kind of wrong things. Also, the child or chilldren know you already, so they might not listen to you even if they get in trouble. If the parents can teach their children as the right way, then why not should the parents be the teachers? Plus, even if they're, kids might think that their parents are nice. For example, my mom was a kindergarten teacher and my mom wasn't mean to me. So, I think that parents are not the best teachers!!