When I was in school it just went to 4A. The top 32 in 4A, the next 32 in 3A, etc.
Problem was schools like mine that tended to be ranked right about 31st in enrollment would be waaaaaaaaaaay smaller than the biggest of the big schools.
But even though the new 7A/6A thing was totally pushed through by schools like Sylvan Hills, I still liked it better the other way. 16 schools is too small for a classification.