I would recommend you strengthened your own grasp of OO-Perl before teaching it. My own OO-Perl knowledge was pretty much gleaned from just two books, Programming Perl (I learnt from 2nd, but having read 3rd wished it was around then), and then Damian Conway's 'Object Oriented Perl'

Unsure about high school-level, it's been a while, but by judiciously loaning this book to people I seem to have inspired a few others to learn OO-Perl fairly well. I know too that when I was being asked questions about it by them then I was able to remember enough of the book to show them where it was in there, and also to talk them through it with my own descriptive commentry.

Having a copy of these (And probably 'Elements of Perl' too) to show to any of the class who seem to be chomping at the bit to get more Perl would probably be a good thing, would help them see what the more-respected books are like and so avoid the less useful 'The Complete Idiots Reference To Teaching Themselves PERL CGI In Sixteen Seconds' books.

Feel free to point them at Perlmonks too, although warn them that you'll be peering at things to make sure they don't ask us to do their homework :)