On October 9, 2008, President Bush signed into law a requirement that insurance policies allow college students who are on their parents health plan to take a medical leave of absense of up to 12 months. This new law DOES NOT TAKE EFFECT until October 9th, 2009.
Under current law, if a child lost full time student status, the child would also lose eligibility for coverage under a parents health plan.
Several states had already passed this provision, check with your local carrier or broker to see if your State already has this legislation in effect.