Television and film each have their own unique Rating systems:
Film: G, PG, PG-13, R, NC-17
TV: Y, Y7, Y7-FV, G, PG, 14, MA
I think Broadway should start to use a standard rating system. It would help theatre-goers understand what type of show it is, and if it would be appropriate.
The idea, although I am sure not original, came to me because a woman who came to see a show at our school was a middle-school theater teacher. They were doing a study of puppets, and she said she was going to try to do a field trip to see AVENUE Q. My, what she learned in 2 minutes time!
"The Spectacle has, indeed, an emotional attraction of its own, but, of all the parts, it is the least artistic, and connected least with the art of poetry. For the power of Tragedy, we may be sure, is felt even apart from representation and actors. Besides, the production of spectacular effects depends more on the art of the stage machinist than on that of the poet."
--Aristotle