Honestly, SAT scores vs. Performance is the type of (mostly bad) research I am talking about.  The SAT is not designed to test math ability.  It's focus is on how likely a student is to finish their freshman year of college and it does that fairly well.  You can do a lot of useless research in this area and it tells you next to nothing.   If you want to predict a highschool students ability in advanced collage math classes you could design a test that did that.  But, people have easy access to SAT data so that's what they look at.<p>If you want to see real and useful research look into how long the optimal study period.  There are significant and useful study’s which suggest 2 hours of nonstop instruction is less useful than two one hour periods with a moderate break in-between.  Yet how many collage lectures follow this approach.