Study Links Winning Football and Declining Grades
In examining the grade-point averages of the Oregon student body and the performance of the Ducks’ football team, the researchers found a relationship between declining grades and success on the field.
“Our results support the concern that big-time sports are a threat to American higher education,” the paper’s authors — Jason M. Lindo, Isaac D. Swensen and Glen R. Waddell — wrote.
via nytimes.com
I'd say anecdotal evidence confirms this study's findings.