Research by Detterman et al.
http://psychology.case.edu/faculty/detterman_doug.html has found large correlations between IQ and scores on the SAT and ACT . Some of the papers can be found online. The new SAT does have a lower ceiling than the older one (used in Detterman's study).
There are SAT-to-IQ conversion tables online for students in 11th-12th grade. I would like to see such a table for younger students. A math SAT score of 700 at 12 vs. 17 translates into different IQs.
I don't agree with the argument that the SAT must have a low correlation with IQ because people study for it. My 8yo boy is studying for the SAT, especially the math section, using books by Kaplan and the College Board. Before preparing he scored in the low 600s on an old SAT at home. Once he is exposed to all the SAT math he should score a bit higher. SAT preparation is over the head of most 8-year-olds and would raise their scores very little. A test can be g-loaded yet also be studied for. IQ will set a limit on how much score improvement studying can yield.
Talent searches and the Davidson Young Scholars program use the SAT and ACT to identify gifted students, so they must still think these tests are valid for that purpose.
