Research

http://web.ebscohost.com/ehost/detail?vid=4&hid=108&sid=87525ec6-89b1-48ee-948f-409fe597b7be%40sessionmgr4&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=eric&AN=EJ860918

The following study by Rebecca Zwick and Jennifer Greif Green revealed that "high school grades and class rank have larger correlations with family income and education than is evident in the results of typical analyses". Therefore, they state that high school scores and class rank are only associated with that particular school, as each administration grades differently. However, national tests such as the SAT or the ACT "have smaller associations with socioeconomic factors". These tests are without bias and are a better gauge of a student's academic prowess. A successful student at his or her high school can simply have the time and money to have additional study.
However, the same can apply towards national academic tests. Students of a high socioeconomic status have the resources to allow them to score higher in these aptitude tests, such as additional studies and practice tests that warrant money that students of socioeconomic troubles may not have. Therefore, this study is not completely credible.