I think Your Disease Risk is a great site for both teenage and adult English Language Learners. It’s from the Siteman Cancer Center, and leads you through simple questionnaires on various illnesses to determine…your disease risk.
I think the best way to teach English is to find-out what people want to learn about, and then help them develop their language skills in the process of learning about that topic. This seems to be a pretty high-interest area to me. Even if it’s less personally relevant to teenage students, they can certainly answer the questions playing the role of their older parents.
I’m adding this link to The Best Health Sites For English Language Learners.