For me, I took the written test, got my permit and rode by myself. I don't remember a supervision requirement but I was also 25 at the time. I do remember from my teenager days that a drivers permit required to be with someone 21 or over.

I rode in, took my test and that was it.

Word of advice: If you have a friend with a smaller bike (a DRZ would be great) - take the test on that. The cones they'll have you ride around and stop within are tiny (like 6 inches tall) and difficult to see from a big bike. This one guy on a new gold wing, temp tags and all dropped his bike.

Well, tipped over... those gold wings have a built in crash cage called "exhaust"