If your school has projectors available another way to achieve this effect is through video and either bring it out into the audience or keep it on stage.
I've done both as a TD/LD for school productions, the easier projection method is against a backdrop, wall, cyc, etc. I works against black curtains too, if the projector is of good quality.
You can build an animation for the Yellow Brick Road appearing or building against the cyc through Maya or even PowerPoint animations and have it run as a called cue through a PC/MAC or other video relay.
If this is something you'd like more info on, let me know.
However, the yellow brick road through the audience is also sounding pretty neat and a fun activity for a class.
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Erik Morris
Artistic & Technical Director
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Original Message:
Sent: 02-19-2014 12:59
From: Robin Christopher
Subject: Wizard of Oz - Yellow Brick Road Suggestions
We used wide strips of bright yellow duct tape and taped alternating bricks on the the carpet of the aisles. My drama classes spent a couple of days painstakingly taping the carpet, but the effect was exactly what we needed. The audience (especially the children) loved that they got to walk on the yellow brick road. We just blocked the journey through the audience and the actors would wind up on stage for the scenes. The tape we used did not cause any damage to the carpet.
Robin Christopher
GHS Theatre Director
Northeast Ohio