I haven't read OEL manga in a while, so I wasn't sure what to expect from Amazing Agent Luna. I enjoyed the work a lot, though I thought the high school drama elements were a bit much. The cast is almost too tight to quite work. We don't particularly see any faculty outside of the science and PE teachers and the principal. Similarly, the school seems to consist of only two cliques - the outsiders, which Luna latches on to, and the bunch of "Mean Girls" which make up the popular clique. There's no social groups around athletics or drama (or any other extra-curricular activities) to speak of.
Now, I understand that most works set in high school keep the cast tight for an economy of characters. Still, even shows like Daria and series like the Harry Potter books (and movies) have a variety of classes that we see, so we get an idea of what school and the instructors are like, before expanding on these characters and their traits as the work goes on.
Consequently, when the science teacher position basically turns into this series "Defense Against The Dark Arts" position, the high turnover becomes even more glaring when there are only so many instructors that we know.