After years the series is finished. I sat down and reread the manga in one sitting aaaaaand I think there was a big overreaction back in the day when certain characters were killed off. I really REALLY didn't care for Transfer Student powers being explained and the story turning meta with those concepts, I'm cool with just 'Transfer Students exist and we don't know much'. Subversions of what to expect happen a bit too often which makes it hard to follow along. There needed to be more breathing room before slaughtering so many characters and going back after their death makes the flashbacks rather annoying. I did wonder if there would be a full reset by the end, but nope the entire cast is gone by the end of it.
I will say the brutality to kill off so many characters AND to do it in such a shocking manner is rarely seen in most media. There's so many series that claim to do the same yet leave lots of characters remaining in the end. Thinking back to Berserk it's crazy how well executed Miura managed to slaughter his cast and not sour the reader. Personally it would've been better to have SOME plans actually play out successfully and have certain characters actually have a reasonable death giving a bit of satisfaction with their demise. The entire series reads like the first big fight where two rivals (Eyeball dude + the flash) face off against each other only to have the fight ruined by a Transfer Student, just over and over and over again. Like the Principal showing up for her big reveal was so bland, don't get me wrong the story was already turning stale with how it killed the Banchou cast but that was a horrible way to handle the Student Council at that point.
Overall I think it's average. Some interesting twists in the series, the big one at the end is heavily foreshadowed throughout the entire series and I think it does a good job with other smaller events (like the traitor reveal)- which are well written. I will definitely never forget the character designs, or a majority of the cast (cough*Kyouko*cough).