Good teachers are wasted on bad students.I wouldn't know.
Why do you emphasize "Substitute teacher". You do realize that even in the Catholic School I went to, "substitute teacher" usually meant, 'Well, let's see what we can get away with now because she'll be gone before she can catch us up."
What we NEED to do is make teaching a lucrative enough position to where people actually want to do it as a vocation.