when i was in sixth grade, i made these paper mache tribal masks that were really fun, but the process takes a few days, because you put it on layer by layer.
so first you get this really thick cardboard and strong masking tape for the "shell" of the mask and you make a circle and some strips down the middle and across so that you can have a place to put the wet paper mache. you can make extra shapes around the outside. then you put paper mache strips ( kind of big strips of newspaper, around an inch or two thick and about 6 inches or more long) on the outside of the shell,about one layer each day. this will probably take 3 days and then one extra day to make sure that it is dry.
you want to make sure that the layer is thick enought so that it is not prone to holes being punched in. and if you really want, you can use some sort of wiring under the paper mache for more support.
then after you can maybe show your class some tribal designs that they can use for their masks(making it some what educational if you have to)
then let them paint the masks. after the paint is dry bring beads and feathers for final touches.
i hope this helps!!!