I was a youth leader a few years ago, and I know that if you make the material relevant, they will be interested.
Despite what one of the answerers says, kids DO want to learn, they are just tired of having to memorize facts and dates and doing busy-work. They've been doing it for YEARS, you know?
We need passionate high school teachers--passionate about their subjects, and passionate about their students.
I know a teacher who has his students do a family tree--isn't that great?! They learn something about their OWN heritage and history, and then fit it into a larger context.
And use music. Nothing grabs their attention like it--and I know you can use today's music--either juxtaposed or complementarily.
High schoolers are just like us--if we can connect something we KNOW to what we have to learn, we pick it up much more easily.
What's going on right now that they care about? I know my son--a senior next year--is disgusted with the state of affairs--the environment, people driving gas-hogs, politicians lying.
How exciting for you! And what a gift to be able to touch young lives in a way that will impact them for years to come.
Good luck!