I remember my son had to read “The Bridge to Terabitha” in middle school. I read it and I thought it was pretty grim with the the kid’s best ever day also being the day his only friend tries to cross the swollen river to their island, slipping her hands from the rope and drowning.
I still am sorry I didn’t tell his teacher what a crappy, depressing book that was.
I did not know about that book and started reading it to my child when he was younger. I had to stop in the middle after reading ahead. It was just too dark. He then pleaded with me to see the movie afterwards. I warned him that it did not have a 'happy ending' and was very sad. He still wanted to see it, so I let him see it with his adult sister.
He was sort of prepared for the ending and took it fairly well. We had to talk about it after though.