An excellent model is Seattle's pub-ed campaign in the early-mid 1990s, to essentially train the entire region in CPR.
Know your audience. Are they interested in learning and are they interactive? Some demographics are, some are not. If possible, get your plan together, and call the principal or teacher and discuss how they think it will be received.
Adolescents like to be "The Hero", and like having knowledge others do not. I'm neuro, so I'm partial to stroke. Its hard to get people excited about curing fat-arse and brushing their teeth.
"How many of you have a family member who has had a stroke?"
"Do you know how to tell if someone has had a stroke?"
"If you can give this information to 911, it may help save that person's life by making sure they receive the best treatment as soon as possible."
You can print these(or save to disc/zip), and get them laminated into pocket cards at Office Depot for probably less than $15. Handouts are always cool.
FAST is quick, easy, easy to present, and can be as interactive as you want.
Edit: T (time) also means the last time the person was known to be "normal", for teaching purposes. you're trying to see if they qualify for TPA.