I would just be zen about keeping it clean. They aren’t going to make masterpieces – a little devit isn’t going to distract from the gee wiz factor that comes from making something from glass
We’ve done projects with schools before where each child gets a 3″ x 3″ piece of clear and a palette of 3 colors of frit and stringer (no sheet glass so no cutting). We fuse the tiles to a single piece of base glass and slump it into a large bowl or platter (which often gets auctioned off as a fundraiser). The amazing thing is that by having all the kids use the same small number of colors the final piece is gorgeous every time.
Helios Kiln Glass Studio