I was a little surprised that the mother hadn't picked up on Lydia's plight earlier, since she later shares that she was accosted by a relative when young, and surprised that the school didn't take things more seriously. I also would have like a bit more information about the principal's family connection to Lydia's house.
Books like this are important to show them that they need to do this in order for things to change. Lydia's experiences will help readers understand how insidious harrassment can be, but also give them tools to help in case they ever experience it themselves. It's sad that these issues still exist, but they do. Even twenty years ago, I told my daughters that no one was allowed to make them feel uncomfortable and that I would support them if anyone did; this kind of empowerment needs to filter into every section of the population, and books like this can help that happen.