Hi,  I am a former high school student and we did Hello Dolly my sophmore year of high school.  Basically because we had a small budget we did our set on moving triangles.  I think we just had 2 of them.  Im not sure how big they were but they worked very well.  It's basically 3 flats put together in a triangle form with wheels on the bottom.  You can put 2 next to each other and have one big wall of seperate them and put a stair case in the middle.  I believe for the private dinning room scene the big triagles were next to each other and then we had a long poll stick out from the center with a curtain on it.  It divided the dinnnig rooms on stage but not for the audience.  THe whole triangle set works really well because all you do is spin it and it is a different scene.  THats about all i can tell you and i hope this helped a little bit.