Vicki's suggestion of weaving is an excellent one. It's sooo-oooo clean
and relatively cheap. You can use colored scraps of matboard as looms
and leave the weavings on them, or use chipboard looms so the students
can take the weavings off. A package of chipboard looms, already slit,
is inexpensive and they are reuseable if you're careful. One word of
advice: buy cones of yarn rather than skeins, which tangle badly.
I taught cardboard loom weaving for many years and I believe some of my
diagrams are on IAD.