Maybe if it's 19 out of 20 failing your little test, you're the problem?
Maybe your question is shit?
You should likely be doing exit interviews and getting honest feedback from your applicants. Because either way, you need to understand why rather than be frustrated at them.
Confidence and cockiness is a trademark of any person fresh out of school. They think they just finished learning everything.
You can choose to stick your head in the sand but it's been going on for a few generations now. "Go to college and you'll know everything to get a great high paying job!"
I can understand why you might think that, but you have no context, so you're making superman leaps there. I own a construction company, we build commercial, residential and industrial, remodels and renovations. I will have people aply for my positions, and they will tell me that they've built houses from the ground up, done years of renovation work, bla bla bla. My drawing test is that I draw them a simple 8' tall wall outline, 24ft long, I then draw a door and two windows, then i ask them to draw the Framing. I tell them not to worry about scale or making it pretty, just show me where the wood goes.
18 out of 20 of them don't know what a header is. I could have done this before I was 12 years old. I don't give a shit about their opinion on exiting my interview.