The Talent Search testing may become meaningless only if you accept that single set of nubmers as the ultimate final word on your child's ability. The Explorer is styled as an achievement test, but I think it is only an achievement test if you are either an 8th grader or have learned 7th grade curriculum.
There is obviously a continuum of grades/ages/curriculum coverages/preparations of the test-takers so the extent to which it serves as an achievement versus an abilities measure may varied considerably. For my 3rd graders, who did not prepare beyond looking at the sample questions in the packet, the Explorer is more of an abilities test than a true achievement test. For example, neither child has studied science curriculum above 3rd grade, but DS scored a 20 while DD scored a 17 as 8-year-olds. As a matter of fact, while DS does have some interest in science/technology (so may have inadvertently exposed himself)DD hates Science and has a decided aversion to all things non-fiction so I know you do not need any exposure to do decently on the Explorer. Of course, I am not saying that DD's 17 in Science is a great score, but that you can do decently (63rd percentile) compared to 8th graders without any interest/preparation/exposure if you have good reading comprehension and logic skills.
Regarding the SAT CR, I have definite opinions as I considered teaching prep courses (SAT/LSAT) part-time ages ago. According to the stats, reading comprehension was the one category that these prep courses were least successful in raising the scores by any considerable amount. Unlike the other areas, there aren't tricks or discrete/limited content to master. Reading comprehension (at those levels) takes a longer period of time to raise significantly than test-takers typically spend preparing. Of course, that may no longer be true as schools now have freshmen take the PSAT and generally make test prep available to all. I am going back a quarter of a century, but it was not so crazy that I did not prep beyond taking the PSAT and took the SAT once. Of course, had I not scored in the 99th percentile, I may have considered taking the SAT again. My situation would likely be unheard of today.
