This massive unit goes into pitch, specifically how to build any major scale using the "formula" and how to break down the math and logic behind sharps, flats, naturals, accidentals, and key signatures.
The goal here is to let students see why scales are the way they are: as in all things with music theory, this is based on math.
I love teaching this unit alongside the piano, so have a visual (at least a keyboard or piano keyboard handout) that kids can use to help them. I give them a copy they can write on for their notes, and have extras available.
I teach the scale formula so that students never feel that one key is "easier" than another. As an instrumentalist, I have a heavy preference to certain keys of course, but I don't want my theory kids to feel paralyzed when they see the key of Ab Major or E Major. The way I teach, every scale and every key is the same level of difficulty, because we are teaching them concepts instead of just blind rote/memorization.