research question

Hi guys, yes, it's me! Not an imposter, no!
I got bit by a plot bunny. I eyed it warily, and I'm not sure if I'll give it a shot, given my apalling habit of neverending my stories, but I ended up asking myself the following question:
What are the academic requirements for becoming a high school teacher in the US? How long does it take to get the qualifications, say as a sports teacher? Or swim coach?
Help would be greatly appreciated. :-)