Or they're a student who has to work a part-time job after school. Or they have a long commute. Or they have hours of practice for a competitive sport or extracurricular. Or they have to take care of their siblings, grandparent or sick parent. Or they were told by their parents and teachers that because they're smart and do well in school that they don't need to worry about studying. Or they know their parents can't afford an elite school anyway, so they know they just have to score well enough to get into a school with in-state tuition and noncompetitive admissions.
Two kids who both went to the same school, were told the same things about the importance of the SAT and dedicated equal time to study and preparation can probably say that the difference in their scores is indicative of differences in intelligence.
But any two random students? There are so many factors that could cause students to underperform their hypothetical max score if they had perfect conditions in the months leading up to the test and day of.
