My son, at age 16, took a College English class. He came home urging me to read his assignment, Martin Luther King Jr's "Letter from Birmingham Jail" which was written to "Christian and Jewish brothers."
As a believer, it is one of the most powerful and moving letters I have ever read, especially in light of who it was writen to. If you are compelled to read it, the link above takes you to an printable pdf of his six page letter.