Are those who are doing ACT/SAT with younger kids (dottie?) prepping?
The main issue with these tests is stamina. They are really long and intense. Some kids thrive on that and others are overwhelmed.
DS took the ACT at 12. He had not taken any talent search tests before. I did buy The Real ACT and had DS take a practice test before we decided to even sign him up. He did OK on the practice test, well enough for us to decide it would be worth the trouble to sign up.
The practice test was helpful for us because DS needed test taking strategies. He needed practice with time management and filling in the bubbles. His state tests are on the computer so he didn't have any practice with the bubbles. We didn't actually have him work on content. He took another practice to test his new test-taking strategies a couple months before the ACT. That was about it. His scores were very good, not the highest around, by above DYS level.
He took the SAT about 4 months later without any practice except making sure he knew the test format since some of the question types are different. He did not score nearly as well on that, but still at DYS levels in reading.
For both tests, I really wanted to know what DS could do without formal test prep, what content he had absorbed by osmosis, so I really didn't want to teach him new information specifically for the test. But for the test to give me a sense of what he knew, I did have to make sure he understood strategy.
Sorry this got rambly. I hope is helps someone!