[haguruma]

Originally Posted by TinyRedLeaf

Actually, scratch that, because come to think of it, there is always someone volunteered to be "non-existent" every year, since they always manage to have exactly 30 students to begin with. The shock for the Class of 98, it seems, would be that they expected to have one empty desk, only to see it suddenly occupied by a late transfer, meaning that they would have to go through the whole rigmarole of pretending someone doesn't exist, only they were one month late, without realising it.

I'd like to step in on that, but only because the important part, that is Misaki's desk, was only discussed very briefly during the time of episode 5-7 where it actually went into what is happening. I will explain this in spoilers (though it really isn't one) so people can keep guessing about it or find it out on their own, but it doesn't matter whether there are 18 students assigened to a 3-3 or 38. This all comes down to a technicality in timing and how schools are orgaized.

Spoiler for How are they a desk short:

The problem is not any fixed number of students in class (though anime in general seems to prefer to have students at a neat number like 20 or 30) but the fact that a desk is missing and an additional desk has to be provided for the "inexistent one". This additional desk is taken from the old school building, which is why it looks so damaged and old.
The size of a class is determined before the year actually starts so the janitor or students will provide the appropriate number of chairs and desks to each classroom before even the entrance ceremony starts. The "one person more" only seems to join from the ceremony onwards, so they go to class and notice "damn, we're a desk short".

And yeah, I'm very happy they're going with something closer to the novel's finale instead of the route the manga took (which was awful because of magical lightning).

EDIT:

Originally Posted by Arya

I know that this depends on when Mei discovered who the extra is, but in theory it would have been a great difference.

I agree that it is a little convenient for Mei to react this way (it provides us with a method to learn about the one person more and still gives room to enough tension..but it seems so artificial), BUT I also understand her train of thought if this were a real person's decision. She probably knows how impulsive Akazawa and some of the other students are. Either they wouldn't believe her and declare her responsible or it would have started a riot and she would have been responsible for casualities that might have been unnecessary.
It is an important question...is it alright to victimize a person (and though dead, that one person more is at least temporarily alive and breathing) to potentially save others?