Depends on what the show is but there's no specific cut off. If they are casting a character and you can play that age than you could be cast. Their website has information about auditioning.
That is a very good question! I don't know the answer. The theater staff themselves would be best able to answer it. I know they have acting classes but the audition process I know nothing about. I very much urge you to persist however. Best of luck!
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