While I don't question your experience, and while I don't doubt that it is replicated in many places, this is not true of all Catholic schools. (FYI, we're homeschooling for this very reason). A good Catholic school is a beautiful thing. A bad Catholic school is a public school with a modicum of religion thrown in. Don't jump out of the frying pan and into the fire.
Morals and religious doctrine should be taught in the home and at church. The main reason for going to school should be to get a good education which will help you get accepted into a good college. In that respect, I think that a good public school can be even better than a Catholic school. The reason why I went to a private Catholic High School was because the public school in my area wasn't challenging enough.
However, that being said, if you purport to be a Catholic institution, you better act like Jesus, and that includes being open to everyone and being a nice person. And no Catholic institution that I've ever been associated has ever been like that. Unlike Evangelicals, who are open to everyone who accept Jesus into their lives, many Catholics that I know will make you wear a Scarlet Letter for the rest of your life, even if you didn't do anything wrong. Unfortunately, this is what the fifteen-year-old girl in question found out; she went against the stream and exposed her school's dirty laundry, so they made her pay for it.