I am not totally sure about the ACT, as my D took the SAT twice as part of the Northwestern program (and we also registered her with Johns Hopkins CTY). But for the SAT, the scores are wiped out at the end of their eighth grade year so they are not reported to colleges. This was actually a problem for us, as we did not recieve an official score report for D's excellent scores (3rd place in Northwestern search for one of her scores last year). Then the scores were wiped out. So just a word of advice, request an official score report from the College Board for your kid's SAT scores before they are deleted!
Regarding benefits, one of the best benefits for us was D's invitation to join the Cogito online community that Johns Hopkins sponsors. It gives her a chance to link up with gifted kids from all over the country.
My D was not invited to take part in the talent searches. A local professor who did some IQ testing on her when she was small had suggested that we look into this eventually, so we just signed her up directly.
D has not yet attended any classes from the talent searches. She has applied to THINK at Davidson this summer. But she will likely do 1 or 2 CTY courses in the next couple of years. The course listings for Northwestern are a mixture of AP and non-AP courses. The CTY courses do not show any AP designations, but they have a lot of interesting topics.
