Bus drivers, especially school bus drivers, suck. They are some of the worst, and scariest, drivers when it comes to cyclists.
My solution?
1) Get a mirror
2) Use it, and be very assertive about lane positioning.
In situations where the road width is less than ideal and there's opposite direction traffic approaching, if I see a bus overtaking me I often move to the middle of the lane, and indicate with a backward facing left palm that the bus driver will NOT be passing me.
Using a mirror, this is a routine maneuver. Without one, you're often surprised by the bus...as in the post that started this thread.
I hate getting surprised on the bike, and find that a mirror (the
Take a Look), provides greatly enhanced situational awareness.
+100
Generally, VC take the lane zealots annoy me, but, sometimes you have to do what you have to do.
That being said, realize as has been mentioned, that they have a schedule to keep. Try to be cooperative. If you must take the lane, do so, but, it wouldn't hurt to hammer it a bit just to show the driver that you are aware you are slowing them, and you're trying to do something about it. And if taking the lane means you will hold him up a bit, why not back off a little wave him buy and maybe catch a few seconds of drafting. One of my favorite tactics is to try to time it so that I can get into his slipstream as he's pulling away from a stop. If you time it right, you can get a very easy 35-40 mph ride for awhile. Adds a bit of excitement to the ride home!!!