Every single one of the schools that I work at has their own garden(s). It's typically the students that do the gardening and usually, each gardening section is divided by grade and class. For example grade 2 class 3 (8th grade class 2) will have their own gardening post and will be responsible for taking care of the plants.
I was at my smallest JHS, which has a total of thirty-six students, yesterday and we spent not nearly half a period planting various flowers. Well, I just walked around taking pictures, but the students couldn't help but question the device I was using. "Is that an iPad?" No, silly kiddies. It's an iPhone. Anyway, I was pretty surprised at how fast they got the job done. There were four gardening posts and the job was done in about fifteen minutes. It wasn't without any mishaps though. A couple kids accidently stepped on the flowers they planted. Oops.