If you want to play classical music to high school students, maybe choose a piece that has half and half, some for teachers and some for students (i gather your playing to students and teachers), Hungarian rhapsody no 2 has a nice slow bit that the older teachers will like, the students may get a little bored but then hit them with the friska and everyone will love it, people recognize this piece even if they dont know classical music.
There is always Scott Joplin Maybe the entertainer. Or maybe some Video game music or TV Themes like the simpsons, everybody loves raymond.
When i play at my school i play stuff like, mario, final fantasy, halo theme, simpsons, and for classical maybe liszt sometimes chopin, i played heroic polonaise and they enjoyed it, i guess because they have heard it before, the students i play for they dont care if its classical or what, they just like seeing me play. Oh they hate slow emotional stuff, yucky. I choose the difficult hard stuff.