It's a pretty interesting plot, it definitely kept me hooked to watch all 12 episodes. Although some of it's plot is pretty predictable, the plot progression is just right, not too fast, not too slow. A lot of people say the progression is too slow, but even then, slow progression just gives me more time to process things. The opening was kind of slow, I'm gonna be honest, but they manage to make the rest of the show interesting. The mid parts were perfectly executed to build up tension and anticipation for the finale, while also giving the viewers time to rest from the carnage. The finale was absolutely great, it was total human disorder, panic and carnage. And it really showed how irrational people can get in such intense situations, they could've executed the drama better, but it was still great nonetheless. The final scenes with the main characters, was not the best closure, kind of anticlimactic. But I still loved it.
The "Plot holes" these low star reviews are talking about, are kind of irrelevant, and they didn't even go to write a full review mentioning all of the said plotholes, because I really didn't see many. "Why don't they just close the school down" well obviously, the extra would just wander to the next school to spread terror, and now to inexperienced students. So that isn't the best idea. Supernatural forces, even in real life, are not ones to mess with.