What to say when dumping a boyfriend?

What do you say when you want to break up with a guy because you want a different one? Well, even though this isn't being fully truthful, I would say something about how you need to concentrate more in school (or whatever else you're into) but that you don't want any hard feelings. There's no point in telling him you like someone else, he's going to be hurt enough. Be as kind as you would want someone to be kind to you. What goes around comes around, eventually;)