At what belt..

[tsukimaster]

In general, brown belt (or one step from black) but if the studnt is above average, showsa desire to assist, and CAN assist. Green might work.

[MichiganTKD]

Depends on the student. I know Black Belts who are entirely unqualified to teach and assist. They only teach because they have a black belt around their waist and the Instructor delegates to them.

 

It is possible for color belts to teach aspects of class (some kicking, basics, form etc.) to lower ranks if they really have a handle on the material and they don't mind helping out. Just because someone is higher ranking doesn't qualify them, however. It takes a special individual to be able to effectively teach others.

[embm]

In our school, generally speaking brown belts and above can attend the instructor's classes. With our head instructor's permission, lower belts will help teach other lower belts. Depends on what is being taught. An orange belt who has his hyung down pat might help another orange belt through the form. Or a lower belt who was a Golden Gloves boxer, might help another student with boxing drills or guarding drills.

[xtremartialarts1]

You could open it up to anyone who is no longer in your beginner class(probably the 4th belt). Then you can start training them at an early age. They don't necessarily need to teach the classes, just hold a pad, keep the kids quite and in line, maybe even strech the class. This will help them develope leadership skills at an early age.

[aefibird]

I started helping out in karate classes when I was a 4th kyu (purple & white belt).

 

Generally, in the FSK, class assistants are usually only brown or black belt, but it really depends on what each individual instructor wants and also on the maturity and teaching ability of potential assistant students. There's no point having a black belt help out with the kids class if they hate kids if a lower grade student could do the same job but much better.