Music teacher didn't let me play drums because "they require rhythm." Proceeded to fill the position with a student who had no rhythm, never learned to read music, and played every song "da da ch da da da ch da da da ch" with the occasional flourish every 4 measures. Brought me in to play the first time we had a big important song for which she noticed that "da da ch" was not, in fact, how the sheet music went. Come junior year, I somehow got roped into teaching drumming to the next set of students during a class I was supposed to be learning while attending.
Her son (a year older than I) and I had similar vocal ranges: we hit about the same low note but I had four or six higher notes on my upper range. He became our baritone and I was the tenor. I end up singing higher than the alto girls at many points. This works to my advantage when I got to All-State Choir twice because I could hit the high note on The Gondoliers consistently, while he never succeeded. (Tenor 2 had a 50% acceptance rate, Baritone 1 had about 8%.) I also had to learn to blend to his tone so as to not overpower him (which, admittedly, is a nice skill to have).
There was an inner circle of students, which you could define as "those of noteworthy talent as defined by the music teacher, yet excluding my family for some unstated reason," who got extra training and focus. It would have been fine, but the day that sticks in my memory is the day the inner circle got jazz improvisation training from an instructor for an hour, then went to all-band class, where the instructor had the inner circle plus me each perform a jazz solo. You read that right: I'd been singled out to perform a jazz solo with nary a second's instruction on what that entailed. I basically facerolled the keys, as you would if you'd never taken a single lesson on music theory beyond what was required to read sheet music, and got a "not bad, though a little repetitive" from the instructor. To this day I can't fathom why I was singled out as the one person to be shoved on stage without training.
On a side note, her son got the dramatic lead in every fall one-act play we did (while I frequently got the comedic lead in our spring play). I badly wanted a dramatic role with some nuance to it, but he kept getting the part, which would have been fine if I was told he was better, but I was continually told he was just more senior and "you'll get your turn." Pointing out that, since I heard this excuse every year, it meant he got four lead roles and, at best, I was getting one (the year after he graduated) did not sway the teacher. Come my senior year, he's gone, one-act comes up in the fall... and for the first time ever we do a comedy.
Looking back, it was a good lesson (in that life is bullshitty like that sometimes), but all this (and everything else from about 5th grade on) really taught me that my mentors and superiors are always flawed (and sometimes petty, stupid, and/or misguided) human beings at their core.