On a serious note

I've been following this story about bullying in a high school, where the girl hanged herself after school one day because it was so bad. I just wanted to share this tragic story. The link is to the story on CNN. It's so sad.
http://www.cnn.com/2010/CRIME/04/09/massachusetts.bullying.suicide/index.html?hpt=T2

What sort of adults would let that sort of thing go on for so long? Wouldn't there be signs? Just so many questions and concerns for my young children.