(Because I was going to run out of time to edit my above post)
An Uni of Penn’s researcher (named Erling Boe) discovered there was a way of determining a student’s math skills before he/she even takes the TIMSS (Trends in International Mathematics and Science Study).
The TIMSS has a tedious 120-questionaire section at the beginning that asks everything from their personality to friends to their views about math. Many students leave between 10-20 questions blank.
He observed that there was a direct correlation between the math scores, and the completeness of the questionnaire.
In other words, students that lacked the concentration to complete the 120 non-math questions typically performed worse than students that could sit through the entire set of questions.
I recall hearing about a college that test incoming freshmans’ math ability, without asking a single math question.