I've been in a classroom with kids from different age groups and found that teens are not the hardest to get to (7th and 8th graders top the list). All of the points mentioned are very good and will definitely help. It sounds like they all want to be there, so basic motivation won't be a factor.

But, with teens, I've found that you still have to reach out and grab them right away. Wow them with an example or two of what they might be producing if they put their mind to it. Now the catch: Try to connect the art with their culture. Sure some will want to shoot flowers and birds and clouds right away. But the majority will need to be shown (just a gentle nudge, mind you) that cars, or athletes, or kids hanging out on the street corner can make really cool images too. Don't tell them what to do. Hint at where they might find some ideas and let them get it themselves.

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