Echo by Kate Morgenroth
Echo is the story of a boy who was present, and perhaps more, at the tragic death of his little brother. A year later, his life is a living hell, and he decides to end it all after a particularly horrible incident at school. This book turns into a groundhog day-like situation with escalating confusion (or enlightenment) about what really happened, both at school and in the original incident. There's a bit of a let down twist at the end with a very modern issue being high-lighted.
UPDATE: At first I wrote that it was a maybe, but I was distracted at the time, and had completely forgotten about the scene that really disturbed me with the gay teen in the bathroom. It was never clear that this scene had actually happened, but it felt exploitative and unnecessary. NAY.