One idea for scenery for an arena stage is a free standing "Flip Book". This flip book will have a series of 10 feet long by seven foot high canvases which are flipped over by teachers for each scene.
For best results, you could place a picket fence in front of this flip chart. These elements suggested here will work just as well for a proscenium production.
Click here to view larger image of the wooden structure
CONSTRUCTION DRAWINGS FOR A FLIP CHART
Click here to view larger image of the construction drawing
Another idea for an arena stage is to get two children to hold bamboo poles with a backcloth draped between them. Here we have used the night scene.
A simpler version would be to use lightweight black or dark blue material, perhaps voile, with sequins sewn on it to represent stars. As the children move the material, these "stars" will catch the light and twinkle. The material could also be suspended between two basketball net supports to free up more children.