Now, I'm not saying that we should know the laws inside and out before you're even old enough to understand boners. But there should at least be prep classes that start in elementary school, in the same way that math classes don't dump you into trigonometry without first teaching you how to add and subtract. "Here's how to not offend or physically hurt people. We'll talk about the more complex laws when you're older and less stupid."
"OK, do any of you fuckers have a dumbass question?"
We already have this system in place with the Constitution test. You learn the basics like the Bill of Rights in early middle school. Then you take a bigger test right before moving on to high school. Then you relearn and retake that test before graduation (usually in your junior year). That's to ensure that your dumb little middle school brain didn't forget all of that information. It's prep, prep, prep, prep ... OK, now show us that you've actually learned this shit.
All of those basic law-centered training programs you have to learn at a new job should be required before graduation. You'd get a certification, just like you do with CPR in health class. Then when you start a job, you could just show them that certification, and maybe take a simple test on the information, just to make sure you didn't beat the shit out of some nerd to pass the class for you.