Actually they not that different from last years criteria. Some up and some down from last year.
http://www.ctd.northwestern.edu/docs/ctd/acscorecriteria2011.pdfIt depends what someone is looking to gain from testing. For us, it was purely wanting to understand DS better and advocate for him better. We did not prep him. We wanted to know what he could really do on his own. Ds doesn't even know about award ceremonies. It is possible to get those scores without prepping. My ds has some exposure at school but even more of his exposure is his own reading and self learning style. I'm sure exposure matters on achievement testing but it doesn't have to be formal schooling or prepping. His scores lead to us getting IQ testing done, our DYS application submitted, and acceleration for next year. It was super helpful for us. I wasn't worried about the Numats stats as much as being able to show the school he was functioning higher than their prep school seniors.
I did find the HS testing more helpful than Explore because school officials are familiar with it. Only a few understood his Explore results.
On prepping, I'm not sure how much you can prep a ND kid and get improved results on Talent Searches. I'm sure prepping a GT kid would most likely improve the scores. The kids have to have a certain level of readiness to teach higher levels. If I needed DS to have scores for entrance to a school or something of that nature. I'm sure I would have considered prepping him. Just like he will prep come college time.
My 2 cents ... The experience was invaluable to us:)