Okay, there were not enough grammar and/or spelling errors to earn decreased stars. And yes, I know its a book targeted for children. This was another walk down "what should I write next" and I had hopes for the story as it unfolded.
First, the stuff going on at the school didn't feel like a secondary plot at all; it totally took over and then flopped because not enough time was spent on it. It was too serious an issue, and too quickly resolved (although it is sort of a cliffhanger on that front, since the reader doesn't know how students will respond to principal's resolution).
Next, I know kid stories are supposed to not have a lot of adult interaction, so the child can have their arc, but strangers stalking and showing up at schools without teachers or staff being superstitious? No! Also, the main plot (based on title) felt more like the side quest, barely having any "page time" (screen time). There really was no surprise affect, cliche plot; even the reveal of why Ms Young did what she did. Mr Johnson just showing up and everything about him was creep factor level 9000 but no one in the story echoed my chills. Odd when reader seems more concerned about the characters, than the writer or characters.
I do like the writer trying to show different diversities and upbringings, but feel more was needed in same scope.