Unfortunately, you can still only enroll in Classrooms that are within your same domain unless the domain administrator has whitelisted the domain you wish to enroll in. Still, this is big news and Classroom has many possible uses in the private sector.
As a 7th grade teacher, I use Classroom exclusively to send out announcements and assignments to my students. On a personal Gmail account, I can now use Classroom with anyone else who also has a Gmail account. Keeping family members informed, distributing material to church groups or other civic organizations. The possibilities with Classroom are limited only by the individual.
