I guess I was lucky. I like to sit in the stands so I spent 4 years of HS varsity ball there and never heard a peep* about my son, and really hardly anything negative about the coach or other players. I mean there were a few people who had their issues but they didn't broadcast them in the stands.
Basketball was different. Our team was not very good for most of my son's four years there; in fact, they sucked the last two. The coach was not super popular with his parents or players, and there was some chirping, and by some, I mean a hell of a lot of it, and when people start chirping indoors, everyone can hear it. I can still hear one mother's voice in my head to this day. Her son was athletic and a good shooter, but for some reason he usually did not start, though he was one of the first guys off the bench. Every game, usually 5 or 6 minutes in, as our guys started to fall behind, she would begin yelling at the top of her voice "PUT KEVIN IN! PUT KEVIN IN! PUT KEVIN IN!" I can't recall exactly what happened, but Kevin did not finish the season.
*This doesn't count because it was a fall ball game, which is not technically HS baseball. A parent of a pitcher who failed to cover 1st on a GB to F3 loudly remarked that F4 (my kid) was supposed to get there.