Hi, Luke,
Thanks for visiting the Apple Support Communities. If I understand your post, you are the Family Organizer of a family share group that has an Apple Music Family subscription. You'd like to transition your subscription to a student subscription, but would like to ensure your family doesn't lose any of their own music in the process. I'm happy to help!
There are two options available to you that should maintain everyone's music without service interruption, and both require each member of the family group to switch to an individual plan of their own to start: Manage your Apple Music subscription - Apple Support.
You can keep the memberships this way, and either keep everyone in the family group (so the family organizer would pay for the individual memberships) or disband the family group so everyone pays for their own membership: Leave Family Sharing - Apple Support.
Alternatively, once every has transitioned to their own Apple Music membership, another adult member of the group can leave your family group to start one of their own, along with a family Apple Music subscription. Once they've done that, they can invite the other members of your group to their family group, and their Apple Music Family subscription: Get an Apple Music Family subscription - Apple Support.
Have a good day!