I teach Economics at our high school, and I have taught for all 9 years that I have been a high school head coach. I think it gives me a great advantage because I have access to a lot of information that other coaches will have a hard time getting (grades, teacher comments, etc.). Also, I get to chat with my players (from 9th - 12th) at times throughout the school day, which is great - nothing like talking baseball after school or before a class with an eager young man.
I think teaching and coaching go hand in hand - even those coaches that are good but don't LIST themselves as teaching professionals...believe me, they ARE teachers!