What percentage of your classes do you teach?
What percentage of your classes do you allow lower belts to teach?
What is the minimal belt you will allow to teach a class? 
You mean for gym owners. I am a bb but I don't have the power to allow or disallow stuff where I train 
My school has 14 grappling classes a week, I teach 10 of them. One of my purples teaches twice a week, a brown once a week and our wrestling coach once a week.
Typically I like purple and above to teach. Our wrestling coach is only blue, but he's a badass and a really good wrestler, just not been doing bjj for long.
You learn the most by teaching. that's why at my school, the Shendokan, ALL students teach BJJ from day one.
Some schools let you roll on the first day, well we let you teach.
yes...i should have clarified...gym owners...or whoever has the power to make the decisions.
Marcelo teaches his classes MWF.
I teach my classes Tue, Thu, Sun.
Unlesss one of us is out of town, there is a Black Belt teaching class.
www.brazilianjiujitsunaples.com