If they didn't misbehave, it doesn't matter if they spend it all, they get another 100k - that's the point. As long as you do your "job" in school, you are living the good live.Even if they didn't misbehave, there would still be students that spent it all. Points aren't just for playing around, also they're for essentials and food. A girl seeing how much she had toward the end of the month might buy jewelry, clothing, or expensive care products, a guy might splurge on the video games.
Class D is full of narcissistic, marvelistic and psychopathic kids (this is clear from their introductions alone). The Synopsis tells us that they are gathered in Class D on purpose.
So it's not that unlikely that the other classes are actually filled with somewhat responsible children or at least children who understand that they are judged by their merit after being told so multiple times (including the speech from their representative)
Why not? It would even work when no first year got any money, because they can look at their seniors which do have money. On top of that 2-D and 3-D will also be filled with garbage, unless you can rank up.Edit: I will concede that this is Japan, where the nail sticking out gets hammered down. A misbehaving student in an upper class who brought the average payout down will get brought to heel, but the little system they set up doesn't work if Class A is the only one with points at the end of the first month. Class D is supposed to be the only fuckup class, right?
We can observe a similar development in schools in real life. Just compare a class with 2/30 bad apples with a class that has 28/30 bad apples
The 2/30 are likely to adapt - the 28/30 will remain the same (unless there are threatened to lose/ by something they actually care about) and the 2/30 "normal people" in the second class will actually change to the 28/30 in most cases.
edit: Now with a... less racist example.
edit2: The thing about this whole "suprise" is that it only works for 1 month anyway, they can probably get by using free products in the shops for now. So it's not like they have to sell their bodies or whatever. Who knows, maybe even the school rulebook has it written down, but no one in their class actually bothered to read it.
But now they know, and it's a question about whether they are able to change and considering that this school boasts with a 100% employment rate etc., we can assume that they will change... or at least develop traits that will help them getting a job.