"The school's policy is that the doors open at 8:40 and there will be no supervision before then, and students are not allowed inside before then. With the first few kids, I was thinking "how rude of those parents to just drop those kids off 15 minutes early when the rules are very clear about when the doors open." However, by the time 8:40 rolled around, there were at least three dozen kids waiting in front of the doors. So now I don't know if this is one of those "we break the rules but the person that made the rules is OK with it" things, or if it was just a SS blizzard. My son was not happy that I wouldn't let him get out until 8:40--he saw his classmates and really wanted to go play with them."
Unless there's a specific rule that kids can't be dropped off early, I don't see this as SS behavior. I presume that the parents who drop off kids know that the kids are going to be outside unsupervised, and so as long as they don't expect that to change the mere act of leaving them at the door for twenty minutes isn't SS at all. Why would dropping them at the door be any worse than having them stand at a bus stop for a quarter hour, and why would you think that "the doors open at 8:40 and no sooner" translates to "nobody is allowed to stand at the door before it opens"?