I'm going to be a senior this year. I want to go to school to become a Music Teacher or something in the music field.
I'm Looking into SUNY Fredonia, SUNY Buffalo State, Nazareth, College of Saint Rose and a bunch more.

What are the major things I should know that every school will probably want me to do. Like what kinds of scales, what songs/pieces do they want to hear, etc.
I play guitar.
From what I've seen, major and minor scales are all they look for.

Depending on the school, you might want to play a jazz standard or a classical piece. If it's a contemporary music school, then a contemporary song might be appropriate.
Only play what you hear. If you don’t hear anything, don’t play anything.
-Chick Corea
They will more than likely want you to be able to,
1: sight read (that means with with real music writing not tabs)
2: be able to play simple scales and will probably ask which ones you know.
3: be able to improvise or keep moving if you mess up

Thats what my guitar and violin teacher both had to do to get in.
From what I've heard, a lot of the auditions center around classical music. Another biggie is knowing all the notes on the neck and being able to demonstrate that. Auditions are pretty tough. You probably should have started practicing for them about a year ago, if you haven't already.
jazz and classical

knowledge of scales

have some piano experience.

be able to read standard notation

have some ear training.
I played violin in college. I guess it might be the same? As I remember I played an assigned piece and a piece of my choosing. I was asked to play a couple scales and sight read. That's it.