Agree. And not just kids. When I met my GF many years ago, she liked to put a big chunk of money from every paycheck into the bank. She was building a nest egg, which is a good idea.
Then she financed a huge chunk of change for a car at 7.99%. She was making her payments, and ignoring me when I told her that saving at .75% while paying almost 8% interest is a bad idea.
She refused to listen, so I let her continue to pay $400/month for the car for about 1 1/2 years.
I told her to call up and see what the payout was. Then I told her to add up all of her car payments to date.
She almost puked.
She paid the car off with her idle cash within a year, effectively earning 7.99%
This isn't rocket science. But as you say...people should be taught.