“If there is such high demand from students who are capable of doing well in the courses, why not reduce the lower level courses (that those students have to take instead of advanced courses that they cannot get into) and reassign teachers for additional advanced courses in the same subject area (e.g. AP US history instead of regular US history)?”
That’s the common sense approach and one that I have been advocating in our district for years. However, when you have a smaller school, I concede that it can be challenging to allocate classes and teachers. I’m not speaking about the OP’s son, who was just two points off of the cut off and regularly gets high As on tests, but sometimes, in order to fill that second section of the honors class that was taken away from the regular version, you might have to put in kids who truly aren’t qualified. That cuts down on the effectiveness of the advanced class for the really academic kids. However, in our school, I’ve regularly observed gatekeeping when there are plenty of good students who could fill up more honors/AP classes and I do not understand what drives it.