I don't mean this disparagingly, just drawing on my own past, but when I was a highschooler, all I cared about was who's having the party this weekend and am I gonna get laid.
My presentations have all been smash hits, but then the oldest members of my audience have been 5 years old [img]modules/Forum/images/smiles/icon_smile.gif[/img] Except for their teachers.
You gotta know your audience and remember they're not all herpers. Loaded questions are tough, and high school people are usually loathe to answer b/c their friends will make fun of them if they're wrong ("you dumb@ss"

or right ("brainiac know it all!"

that's just the way they are.
30 minutes might be a little too lengthy. Try paring it down to 20. Another good idea, if possible (and safe) is to move around the class with a serpent while talking. Those who are genuinely interested in what you have to say will still listen, those that aren't will still have something to keep their attention. But this may not be feasible with a 6' RTB. Caution is the word of the day here. I have a corn snake (3.5') that I'm sure I could swing by his tail as I walked through the class and he'd still never bite. He's my presentation star.
[addsig]