One of my favorite features of GURPS, lately, is a relatively cheap Advantage (sorta like a Feat) called "Common Sense". It's very simple: if you're about to do something STUPID (emphasis theirs), the GM can tell you that you should probably reconsider your actions.
And yet, I had to mention it several times for one of my players to consider taking it.
Look, I'm not gonna tell you the DC so you can just make a note and come back later knowing you can pass. You're gonna have to see what happens and figure it out. The only time I will ever tell a player they can't do something, is if they are trying to do something that is against the rules of the game. I might inform them of potential consequences of their actions if they don't seem to quite understand something that should be obvious, but that's about it. I also use critical fail and success with skill checks in my games, to make things more interesting. So even if the DC is impossible, a NAT20 may still get you through.
if they're int/dex/str, I make them roll a wisdom check to see if they do something impossibly stupid.
if they're wis or cha, they roll deception against themselves with disadvantage. It's excellent seeing a character literally deceive themselves into doing something dumb.
When you fail the history check, and recall your teacher mentioning something about Karsus's Pulley in the year -339 DR. "Can't for the life of me remember how he managed to kill magic with the thing..."
