This movie is about Bobby Kennedy's assassination in 1968.
If you read the comments on imdb, it's as though everyone had a different ending to the sentence, "but obviously the best part was..."
This is an extraordinarily well-done period piece on a very difficult time in US history. I think it's important for students to see, but the themes touch on real issues of the time: there's drug use, and swearing, and extramarital affairs, and alcoholism, and everyone smokes, and racial violence....But the message is AWAY from those, not towards them.
Political conservatives might feel it's politically oriented, though I think the vast majority of religious conservatives will enjoy the social messages delivered through speeches.
Mature or urban teenagers will "get" the themes, but might be confused by the context. Luckily the movie is so good that parents can see it twice.
The other thing - adults cry, a lot, at this movie. If your teen will be freaked out in a room full of crying adults - wait until it's on DVD.