My first big opportunity to join something that required a uniform was Girl Scouts. My 1960's Brownie uniform was exactly as pictured, except for the ankle socks. I was a knee socks kind of girl. I'm sure my parents could ill-afford it, but I was allowed to have the whole kit and caboodle. I happily wore it every Wednesday to school, even on picture day along with the rest of my troop, consisting of all the little girls from both 2nd grade classes in my elementary school. Little brown felt beanie with the Brownie logo, how I loved thee. After third grade I went on to Junior Girl Scouts. Hated the tie, but there was somethingu about that sash with all the badges I accumulated. For some reason our troop split in half in 6th grade, can't remember why, but I assume it had to do with adult in-fighting. After that, it was Junior High, and most of us dropped out at that point. I was a leader for my daughter's troop for a few years, but by that time neither leaders nor kids wore uniforms.
There were no organized sports teams for girls in my home town. Other than gym class, there were relatively few opportunities for girls to do sports at all until high school. My elementary school gym teacher was 100 years old and likely invented field hockey. She had been the high school coach in the 1950's, so naturally we were introduced to the sport in 2nd grade. No wonder I hated it. We used pinnies for that, also for basketball, the only two team sports we girls had. Think of a sort old fashioned apron just like great-grandma used to wear. It was fun in elementary school, but by the time we hit junior high we were over them since they were never washed and smelled bad.
Junior high school gym suits were a horrible uniform experience, as was junior high in general. Gym suits were largely viewed as a punishment, and I never understood why they were required. Color coded by class, they were one piece, snap-up-the front cotton/poly nightmares in navy, cobalt, or pale blue depending on which grade. They required ironing, something we were graded on. Many of the smaller girls rolled the legs so they looked like bloomers, not a look I could pull off.
High school sports did require uniforms. Field hockey was actual kilts, and white blouses with numbers on the back. I was terrible at field hockey, and wearing a skirt on freezing November days was not any kind of fun. I was a JV basketball player for 2 years, but my heart was not in it. Those uniforms were the same as field hockey, except the kilt was replaced with a plaid culotte thing, I suppose now you'd call it a skort. For softball we were given t- shirts. I was a catcher so I wore long pants, I don't think we were even given hats. Nobody came to our games, anyway.