Some people believe that in order to understand algebra you need to be at a certain developmental level, one that generally occurs in early adolescence. However, exponents in and of themselves aren't algebra--though it's possible that the person you were speaking with didn't know this (I'm not joking).
What can be inappropriate when kids are skipped several grades are the level of executive skills required, so organization of materials, writing out work completely and properly, dealing with homework, that sort of thing.
