From my experience, school drivers are about as good or bad as every other driver on the road, but I feel like each infraction they commit is more egregious because of their position. I feel the same about transit drivers.
No, you can't rely on them for your own safety. You are responsible for your own safety, and you have to take measures to mitigate the risk to yourself when you're travelling alongside motorists. I do not trust any of them to do the right thing when it comes to my safety.