dear sir/ madam
Dear H. - Let me start by pointing you towards the American Society for Aesthetics. They have a really good teaching resource page here: http://www.aesthetics-online.org/teaching/. I also can recommend the book Puzzles about Aesthetics: A Casebook, edited by Battin, Fischer, Moore, and Silvers, widely available online. I'm not sure all of the book's commentary will be suitable for high school students, let alone younger ones, because it is a sophisticated introduction to the topic. But many of the cases there would work very well in those classroom settings. Finally, I think the best way to start a lesson on aesthetics is with the students' own aesthetics experiences, perhaps by asking them to share or write about the music, tv shows, books, outdoors experiences, etc. that move them most. Good luck!