Our Project Runway class took a field trip to the local thrift store and purchased many clothing items that can be turned into ???? (imagination- no limit). Sweaters, using the bottom ribbing, can be turned into mittens. If you are going to make them, trace your hand and make sure to include your wrist. Think about the widest part of your hand...will it fit through that wrist opening? If in doubt...widen the wrist part of the drawing. Add seam allowance and cut four. Sew.
If a student prefers, or if you lack the materials, then use polar fleece or old wool blankets. Be aware that the wrist opening will need to be even bigger than you think, because there is no stretchy ribbing to work with.