Every ATA Black Belt Instructor undertakes years of rigorous training before earning the title of "Certified Instructor".
The Instructor Program of the American Taekwondo Association not only includes intense physical training, but extensive training in teaching skills and curriculum management.  One can tell the level of the instructor by the "Collar" they wear.

Red/White/Blue Collar - Jr. Leader Program
Solid Red Collar  -  Adult Leadership Program
Red/Black Collar  -  Certified Trainee Instructor (apprentice program where trainee had logged at least 100 hours of assistant teaching, and completed the first level of the Instructor Program curriculum set forth by the American Taekwondo Association.
Black/Red/Black Collar  -  Specialty Trainer  ( Trainee has logged over 200 teaching/training hours with practical teaching experience.)
Solid Black Collar  -  Certified Instructor