Both dramas have a similar plot, yet, gives off very different feelings. If you like either one of them, I suggest you watch the other one too <3
Both are school dramas about the importance of friendship. Both dramas have really different but interesting story,
They are both school horror-ish dramas. Both are not scary to the point it scares you however they both give a similar feeling so if you guys liked Nightmare Teacher, I suggest you guys to also try watching "Remember, Hari", it's available in Youtube with Eng Sub under the title
All For One is legit underrated. However, if you guys like Idol Producer or Qing Chun You Ni, I am 100% sure you guys will like All For One. Instead of competing in person, they compete in teams and there are no evil editing so I'm sure you guys will enjoy watching both shows ^^
Both dramas are situated in the late 90s/early 00s and they both give the same vibes. If you like one of these dramas, you won't regret watching the other :)