SPOILERS
This is just stupid. All along Misaki knew who was the dead one and acted like she's part of the furniture, not someone who could communicate. Ok let's assume she didn't want to talk about her eye, but she could've said about her assumptions/thoughts all along, like the seats are just as much as needed, there is no lacking seat for a student, like where else has anyone seen a teacher's helper? that's not a job, and like the dead one are blurry or look weird in the pictures.
Even if we leave these, in a sane world that class would've been shut forever for already two decades, as no adequate parent would let their child study there, they'd take the child to another class or school after hearing the rumors about all those deaths and curse.