Not to be confused with his later series, but a sictom that ran from 1969-1971 where he played a gym teacher at an L.A. high school. It actually made the list of top rated shows for its first season but the reason for its cancelation the 2nd year is not clear.
I read once that Cosby didn't wish to use a laugh track and NBC decided to pull the plug when is contract was up because of that and the other was the ratings took a big dive the 2nd season.
Here's an episode.
http://www.youtube.com/watch?v=MBOyyoMcSEM&feature=related