If nothing else, I think that it would be helpful for a bright child to be exposed to testing that can actually be a challenge and to have some idea of their growth from year to year. DS and DD both took it in 3rd grade and in 4th grade. For DS, the test was a challenge in 3rd grade but by 4th grade the test was no longer difficult so the results reassured me that he was developing academically.
Keep in mind that grade equivalents can be less than worthless even when you are using a test able to assess higher levels. A student at 50 percentile in reality is very low as the gap between 50 percentile and 95 percentile is huge. For example, on the MAP reading test, a score of 223 is 50% for grade 10 but you need a score of 224 (1 more point) to hit the 95% for grade 4. The gap between 95% and 99% is wide as well. You would need 236 to hit the 99% for grade 4.
