Gym was a complete waste of time.
I can see where one might think that. But actually, breaks in the book learning are needed. That, more than getting some much needed physical activity is why I think gym ought to be part of the daily routine for every school kid thru at least middle school/junior high.
Recess for elementary kids is great. This is something completely different. Our school day was divided into six periods, so for 1/3 of students, it's either first or last period, and not even a "break." Just an appendage. In schools that do block scheduling, the number rises to 1/2. At least at my school, there was never much physical activity either. Like every other class, activities were planned to hit at about the 25th percentile of achievement student. The first 10 minutes, you had to change into the uniform. Then the teacher had to take roll and note who changed clothes and who didn't, which constituted the entire grade. So, we had maybe half an hour of standing around with some badminton rackets or doing the Macarena (I went to school in the 1990s) before it was time to change clothes again. It wasn't like it was mentally scarring or anything, but even a 13 year old knows when you're wasting his time.
Granted, block scheduling is a horror and ideally the gym teacher should have eir planning period in either the first or last period of the day to avoid precisely the situation you complained about. (In high school, the gym teacher/football coach had first period as his planning period and in sixth period he had PE II, which was basically a warm up period for jocks who had after school sports to be a part of.) We had more varied activities than you apparently did and it wasn't geared to the 25th percentile as this was back before the idea of never use a discouraging word to a child had become so prevalent. I was pretty much a straight A student in school, but I usually got a C, C+, or maybe a B in PE, but I earned that grade and wasn't at all resentful of what for me was a low mark.