My eldest took both her junior year. She did some prep for the SAT, but just took one practice ACT test to get an idea of the questions and timing.
Her SAT CR+M SAT score was equivalent to a 33, actual ACT was 32, and three part SAT was equivalent to a 31 (didn't like the writing section on the SAT). She thought the ACT was all stuff you should have learned in school, especially the math. Math is definitely her weak point, but her highest subscore of 35.
My 10th grader just took the SAT, just to "see her baseline score" (errr, why not prep?). Her three part score was 97th percentile, slightly higher than her sister's three part superscore. It will be interesting to see how she does on the ACT, because she is really good at standardized achievement tests. However, she is clearly more of an abstract thinker than her sister, so I can understand their SAT scores.
Some kids see a big difference in ACT and SAT scores, some don't. The good thing is that all colleges now accept either test, so he can just go with the ACT for college applications.
