My wife teaches an all-day kindergarten class. When I was in kindergarten back in the 70s, half-day kindergarten was mandatory, and few people had an all-day class, unless they went to a private school.
For me, kindergarten was a place where you learned to hold a pencil, write letters on paper (AAAAAaaaaa BBBBbbbb...), draw, stand in line, take your turn...act like a socially correct being who doesn't solve all disputes with head bonking.
These days, the thinking seems to be that kids need as much education as possible before starting first grade, so my wife's kids are writing short reports on field strips and such. They're really more advanced than I was at that age.
So what did I did I do with my day after noon, when the big yellow school bus took me home? Far too much television, for one thing. There was Speed Racer, the Japanimation cartoon about a guy who drives a car. And Bozo the clown.
After those were over, I'd round up two friends from across the street, and we'd dress up like superheroes and ride our bigwheels. Dressing like a superhero involves wearing colored jockey shorts OVER your pants and clipping a towel around your neck. If you wanted to be Spiderman, you also put the colored jockey shorts over your head and peeped through the leg holes. The crotch was right over your nose.
The older kids in the kids in the neighborhood harrassed us about this, which we didn't quite understand. If you were wearing the right clothes, you WERE a superhero, right? Obiously the older kids were villains we would defeat.
Sometimes we ventured onto a nearby golf course, found rocks we liked and put them in the hand-cranked golf ball washers to make them look nice. The golfers bitched at us about this, so we made sure they weren't around when we did it.
There was a girl a few doors down from us I occasionally played with. She had a police play set, including handcuffs she used once to "arrest me." For reasons I didn't fully understand at the time, I like being being in her custody. I went back occassionally--I guess I had a high recidivism rate.