Overall, this is a good time kill I found upto and shortly after the girl got kidnapped the show was really good. But after that it kinda gotten stupid.
One of my biggest problems with this is the teacher does a complete 180. Like it was interesting at first because at first it was kinda funny seeing him actually try to get fired. Then it gotten somewhat interesting in how he basically thrown out everything the kids know. But beyond the kidnapping. Everyone is more than less on the same knowledge level, he isn't doing funny stuff, and it turned into yet another story told thousands of times.
So before the kidnapping I would give this a 9 out of 10. After, I would say a 4 out of 10.