The en-dash is primarily used for both a minus sign and to indicate ranges in numbers (from 2–3 days). The em-dash is used as a kind of parenthesis (I am saying—not for the first time—that I am mad).
On a Mac you make an en-dash with option-hyphen, and an em-dash with option-shift-hyphen. I haven't used a PC for this kind of work in at least 10 years, but I do recall that entering en- and em-dashes was a hassle.
As a parent of teenagers and a middle-school teacher I can tell you that this is a great idea. Try. Try getting teens to talk. Try getting them to talk about important matters. Try getting them to talk about suicidal thoughts.
It's not easy but it does work and it does help. Teenagers who feel this way are usually desperate for the chance to talk to about it. The first thing they learn is that they are not the only ones who feel this way. This is half the battle, sometimes. Often just the fact that the teacher/parent/adult is trying means the world.
And keep trying. Don't stop trying just because the standard line is that it's impossible to get kids to talk about important matters. That attitude is half the problem.
I think this would stop 98% of spam calls that I get. It seems to me that there should be an answering machine with multiple mailboxes that can provide this feature (If you're calling for Pete, press 1, for Pattie, press 2, etc.), but I can't seem to find one.