I'm glad you used the word "encourage," because to be honest, this question sets off my "get off my back, woman!" alarm a little bit. Remember, the myth of the well-trained boyfriend is a dangerous one; you can't live your boyfriend's life, or make his choices.
That's what marriage is for. ZA-ZA-ZING!
Seriously though, don't push anything too hard. I mean, if your boyfriend's a deadbeat, that's something that should be addressed: through direct and caring conversation, through a quick, clean break-up, or even through subtle manipulation. They're all good.
If you do go the manipulation route, the trick is to keep things positive. Never say things like "you should go back to school" or "where's that rent you owe me?" Instead, try things like "you're so smart; I'll bet you'd blow through those classes" or "I find that you taking 12-20 units at a venue of higher education makes me super horny."
Okay, that's not that subtle, but you get the point.
Almost no one on earth will agree with you when you tell them what they should do to improve their life, or what they're doing wrong, ESPECIALLY a loved one (those assholes).
All you can do, and all you SHOULD do, is plant seeds. Let him know how much higher the average salary is for college grads. Encourage him to pursue a dream. Let him know you'll be there for him, as a study partner, as a distraction, as whatever he needs.
But you have to leave it up to him to make the final decision, or you'll be making all of his decisions from now on, and trust me, that gets old fast. Boyfriends aren't puppies, and you can't rub your his nose in it when he gets resentful of your control and cheats on you.
Well, you could, but I don't think anyone involved would enjoy it.
You may have to ask yourself the Reason for your Need for him to go to school. Is he a productive member of the house now ? Does he say He has educational desires that he isn't pursuing ? If education is really important to you, thats great but the reason is just as important. Many adults that did not go to college have Higer paying jobs than some with Masters degrees out there ! What if He "encouraged" you to lose weight or do something else that you aren't currently doing? Would that send a message that you aren't good enough now ?
Yeah, I agree with Stella (and Swaim, of course). This is a dangerous area, tread carefully. If you think it's really important (i.e. he has real potential at a dream job if he goes back to college, and at the moment he's laying around the house/working at the supermarket) then tell him how you feel about it. Try to do it in a light-hearted way, rather than really serious and intense. I don't mean make a joke, but try to talk about it as if it's not such a huge deal. If he still doesn't want to, then do what Mr Swaim tells ya. Or leave it. Can't live his life for him.
Um losing weight and going to school are two completely different things