People should have at least the absolute minimal foundational knowledge, i.e. highschool level. Coupled with that though, needs to be learning the process, the scientific method, and learning how to apply it. Unfortunately many people seem to think of "science" as a bunch of facts irrelevant to their daily lives when it is just as much a process and a way to understand the world.

What it really comes down to though, I think, is a loss of curiosity and wonder. Children are great at this: "why is the sky blue?," but something seems to get lost as people grow older. If people kept this curiosity and coupled it with critical thinking skills and the ability to evaluate evidence and accept the fitting conclusions then we'd be much better off.

People need the ability to reevaluate what they know. Sometimes you are wrong, and that's ok! Scientists are wrong all the time, but that's how you get closer to being right: you eliminate possibilities until you are left with an explanation that you can't disprove. That explanation will have to do until somebody comes up with a better explanation. Then, you have to know whether you should accept that new explanation or not. How do you do this? That's what scientific literacy should enable.