This manga was not bad, but it wasn't really all that good either. The setting seemed like a realistic small town, but it seemed like everybody in it was a violent psychopath. It seemed like this was supposed to be a message about bullying, but the middle school-age bullies are so cartoonishly evil that it's impossible to take the story very seriously. On top of that, (pardon the probable spoilers) the only villainous characters that ever show anything even remotely sympathetic or even human do so shortly before or as they die.
The other reason this doesn't really work as a message about bullying is because most of the characters that are victims of abuse are just as bad, if not worse, than the abusers. I'm not even sure what the thing with the teacher toward the end was about, since it didn't actually factor into the story in any way and just seemed like trying to fill page space.

Aside from that, the story did accomplish the goal of making the main character and her family sympathetic, even if the author had to go to insane lengths to justify what ends up happening. Despite that, I still ended up feeling bad about enjoying the later action, because I couldn't shake the feeling that on some level, this story was just the author's excuse to show children mutilating each other and the message about bullying was just a vehicle to make it a bit more palatable.