I personally think Shakespeare himself isn't overrated, but in a modern context his plays are. Sure they invented/popularised certain archetypes and plots, but they are still pretty derivative in and of themselves simply because I don't think they have aged that well.
When I did Drama in my first year of high school we performed some horrible play that I'm pretty sure the teacher wrote about students making amusing comments to a teacher. That was the whole play. I haven't seen many good plays firsthand living out in woop woop, most of the traveling performers that come to the high school perform "wacky" takes on Romeo and Juliet or motivational speakers. Most of the plays I know of are also musicals (like Bran Nue Dae and Grease), and I'm not sure if they'd work without the musical aspect.
Macbeth is probably one of the easier Shakespeare plays to do (none of the parts are particularly complicated to perform, falling into some easy archetypes to act: feverish and guilty, cackling crone, heroic etc.), and although I think it has become cliched, I think it's still a fairly good story with some fight scenes and death scenes which are always fun. And as with all of Shakespeare's plays there is an updated version written in 'modern' English, which probably makes it easier to memorise. The updated version I read overly simplified it (I think it was too make the original look more descriptive in comparison) so maybe revising it a bit so it doesn't sound silly would be good, unless you find a good version.
Amadeus was a great movie that apparently was adapted from a play, I'm not sure how well it would downscale to a high school production, but that was a good story that could be good.