I agree with Vince's setup. I can tell you it is very difficult for many of the sixth graders in the 12&U group to wrestle the seventh graders who have been wrestling with their middle school programs all year, same as he mentioned with the eighth graders going aginst the high school kids.
I would also add that the date of the age cutoff needs to be made closer to the actual season dates. How they ever came up with Sept. 1st, I have no idea. This means, for example, that there are quite a few kids who are already 13 when they wrestle the first tournament of the year in the 12U bracket. I would think a cutoff date of Dec. 1st or even Jan. 1st would be more realistic.