My HS did Into the Woods, and that worked pretty well for a sizely cast because it has a lot of different leads. I personally don't like it, but Working is another show a lot of schools can do because it has a lot of parts. I agree with the people who said Ragtime as another excellent suggestion because, though it's a little long, I think it benefits from having a big chorus on top of having a lot of principle and secondary characters.
"I thought that that was just going to be a like one shot deal for me, you know, but they kept talking about it like, 'when we do the production, when we do the production', and I was like, 'yes, yes, when you do the production, cool, I will come and see it'". - John Gallagher Jr. on SA