Yes, he is a strict teacher. And I think we discussed Ms. Fink & Ms. Sweetwater...their classes are the epitome of "kindergarteners in 3rd grade", yet Mr. Ratburn is a "high school/college level teacher teaching 3rd graders". (I also happen to think this is a reference to how mature the 3rd-graders act for their age.)

Anyway...giving a quiz on the first day of school? "(X24)5=(1/2)ME3"? Well, if you ask me, that is meant as sort of emphasis of how hard some teachers can be. Obviously, no 3rd grade teacher in real life would assign anything like that. I think Mr. Ratburn's teaching is supposed to parody the way some kids see their teachers- as burying them in piles of homework. Kind of adds humor to the series, to a degree.