Bitcoin can be difficult to explain but so can money and what teenager really knows how that works, hell most people don't know how money really works.
The lack of understanding in money is dating back a hundred years ago. True that money is a medium of exchange, can be earned through working, and having a lot of it makes you rich. These basic understanding in money leads to make the elites who own the banks to be more greedy. People don't know that the money they have is not really theirs in the first place. It is a government owned pieces of papers that when they decided its value to be zero, then what you taught that the money you owned to be valuable is nothing but a piece of paper now.
I think a teenager would probably be the easiest generation to teach bitcoin to, you don't need to teach them the whole in's and out's just a bit about public/private key pairs, sending/receiving addresses and secure coin holding and they will pick up the rest very quickly. 
Still it depends on the teenagers, when they are desperately want to earn then and help themselves and their parents then they will learn in no time. There are no excuses for people that want to succeed. True, teaching the fundamentals is very important, it will serve as a guide for them to be able to achieve the path on what are they going to do in bitcoin. Bitcoin is not just about earning, who knows the teenager you guided wants to be a programmer then his life will be better than me because I'm just into writing and posting. Were lacking a lot of great programmers here. The rest is up to them.