I'm a teacher and I have a Lowepro Compuday 150. It's an everyday work messenger bag with all the pockets and dividers I need plus a clever side padded zip up pocket which is perfect for my Olympus EM-5. It'll also fit a K5 and a ltd prime. It means I always have a good camera with me.
http://www.thephoblographer.com/2011/06/23/review-of-the-lowepro-compuday-15.../#.VeQk8IoViUk
They're discontinued now but you can still get them, and at bargain prices. I love mine so much I bought a second which is stored away for when the first one dies. But there's no sign of that yet.
I also have a Domke F 832 which is fantastic for travel but too big for day to day work. There's also no pockets for storage of knickknacks.