SQL DB Permissions so anyone can modify the DB I'm teaching a class on SQL Server 2014, and want students to be able to restore a Db I give them and then be able to take ownership and modify tables, and also to view the database diagram. Apparently, the diagram part is problematic.

The students will have a local Windows administrative account on the lab PC. If I make the guest role a db_owner will that allow students to take ownership? If not, what strategy can I adopt to give them full permission to, among other things, the database diagram?
Add the Windows Group, Everyone, to the database db_owner role, if you're really certain you want anyone and everyone to be able to do anything they like to the database. Take a backup of the database that you will then distribute to the class. After you take the backup, remove the group from the db_owner role.

The only gotcha is the students need to have their instances configured with Windows Authentication enabled. 

Windows Authentication stores the SID of the Windows principal in the database; in the case of the "Everyone" group, the SID is the same on all Windows machines.