"Are they covered?"
Well, that depends.
The Insurance Information Institute recommends:
1 - Create a “dorm inventory” to document what’s leaving home. Too much bother? Needn't be: just use their handy (and free!) widget. And yes, there's an app for that (available at the site, for both Androids and iPhones)
2 - Check homeowners or renters policies for off-site coverage. Many homeowners and renters policies include coverage for personal belongings even when their off-site (such as residing in the dorm with Junior).
As always, check with your agent for specifics on your policy, including things like jewelry and instruments. You'll be glad you did.