ACA instructors need to know how to properly register classes, report injuries, and complete class report forms. This was covered in ACA Paperwork.
As a general rule, I get all of my students to preregister for classes I teach. This enables me to recruit the necessary helpers and complete as much of the class report form as possible. Preregistration is also useful since you have student's contact information which enables you to change venues in an emergency - something I personally had to do when the road to Lock 5 was cut-off for an unannounced event.