I think the best way to foster humility of knowledge, as you call it, is to create an environment where things must have sufficient evidence before they're presented as fact. For instance, lots of math curriculum simply tell kids the pythagorian theorem without ever making an attempt to prove it. Imagine how different history class would be if, instead of reading out of a textbook in 5th grade and accepting everything in them as fact, we were given a collection of primary and secondary sources and were told to come up with our own ideas? Sure, it would be ridiculous to expect little elementary or middle school kids to be able to do that, and I am no educator. But I think if we tried to foster that attitude from the very start, where everything has to have evidence backing it, people would be more receptive to new knowledge and would base their beliefs upon reason more often.