Except they haven't, in many cases. . . School doesn't end until-- school ends. A kid can't assume that, if there will be no more "work," that school is done.
As a high school teacher of mostly seniors, I can tell you how frustrating it can be when kids (and colleges) act as if seniors are already done. Not to belabor the point, but it's done when I say it's done (which is the last day of school).
Actually, it's over when the Board and the state say it is, not you, and that's essentially a rule made by non-educators. Not to diss you too much but forcing a group of students who are essentially done to hang in there for a few more weeks is just plain a waste. Like your last two weeks of classes will impact their lives so much more than the other 40 some odd weeks you had them.
That said, the entire second semester senior year is close to an absolute waste. Once kids finish their AP exams in early May, the wait is interminable. And almost every kid going to college knows by April where they are going.
Lots of schools here (fairfield county) are experimenting with service weeks, at least give them a positive direction if you're going to keep them enrolled after they are effectively done. Hmmm... maybe there is a general consenssus how dumb the last weeks of school for seniors are?
So the fact that these kids can get started acclimating to college and begin courses instead of waiting a few silly weeks wasting time is great.