After speaking with the very nice mom I told her I would probably put bands on a few more chair legs in the resource room, so the student would not feel singled out from among his classmates. Theraband doesn't grow on trees so how to provide something with a similar function, but free?
Voila! Those t-shirts I've been slicing up all fall might do the trick! This morning I wrapped a 6" wide band of the t-shirt around one leg of the chair, then pulled with all my might to stretch it across to the other front leg. Then, both ends of the strap were secured to the chair legs, using Vetrap (AKA Coban).
Update 12-12-2013--needed to redo the Vetrap this morning since one side was sliding down. Made sure the Vetrap was contacting the chair leg several inches above and below the band.
Update: 3-2-2014--My teacher buddy informed me that the student frequently wound the family-supplied band around her feet while sitting, causing a potentially dangerous situation when standing up without first unwinding her feet--several "reminders" had not improved the situation. Eek!