TL;DR Teaching is a terrible idea if he doesn't want to do it, tutoring would be right up his alley. Without a teaching certificate he can't teach squat in public schools. Without a clean background check he can't teach squat at private schools. $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

give back to a community that has treated him well.

You don't justify this at all. You say he is smart, articulate, and made money. I am with you. But I don't see the treat him well or the community part. And even if they did, so what? Why does he need to do something that he doesn't want to do just because some people in the past did what they wanted to do and he was the beneficiary? And the community you speak of has definitely changed members in the meantime.

I am adamant

So what? Why do you get to decide what he does with his life? If he doesn't want to teach that overrides everything. It's not like a greeter at Wal-Mart. You don't just show up because you need something to stave off boredom, or because your child insists you get a job. He has money, if you want him to give back, let him give that. But don't try to force someone to teach teenagers just because he has adults listening to him at parties.

You bring up teaching, and also volunteering. These are two very different things. One requires a background check, a TB check, and possibly a minimum of training. The other requires that plus a teaching certificate. which only comes after years of classes and weeks of student teaching. You don't just undertake that because your child demands you give back. The only exception to this is if he gets involved in a private school. There he only needs a degree in his subject. So a B.A. in Math would allow him to teach math. You say he has a B.A. in business. Then he can teach business. Period. Nothing else. Not even Econ. Maybe he could get a special waver in some states as a temporary measure, but that is about it.

Based on what you say, volunteering or tutoring is the way to go. He can focus just on the subjects he loves, it will be one-on-one or small group, and most of the students he gets are going to want to be there. Teaching a class well requires classroom management skills, a bunch of students that don't want to buy what you are selling, mandatory reporting for abuse, bitching parents, and a shit ton of paperwork. It is not glorious. There is a reason so many people burn out so quickly.

Finally, from what you say his focus would be much better applied with college students. In a high school he will have to work his way into higher classes. In the beginning it will be showing that x+y=y+x or that the sum of the angles of a triangle all add up to 180deg.

And double finally, why not show him some websites online where he could use his expertise. He could make videos like the dude in Khan Academy, or get on Yahoo Answers. He just needs to find the right community where he could be a resident expert. That he can do from the confines of his comfy couch.