Scott, I think the fact that the actors were well out of high school serves the movie. If Grease had starred teenagers it would have been considered a kids movie like High School Musical, and long since forgotten. Just picture Leif Garrett(then 18) and Marie Osmond, (then 19) playing the leads. Would anyone still talk about this movie in a good way 30 years later? The cast adds greatly to the timelessness of the movie, even though on paper they seem miscast.