It may be one of the last socially acceptable put-downs, but pointing to research Cognitive Daily suggests "dumb jock" may just be a stereotype. After controlling for a number of variables there is a small but statistically relevant correlation between athletic participation and academic achievement.
[Herbert] Marsh and [Sabina] Kleitman claim that their study resolves some, but not all ofthese methodological problems. Though a longitudinal design -- following the same students for many years -- can show if a student's academic success is associated with athletic participation, it still can't demonstrate that some other factor isn't responsible for both athletic participation and academic success. It can, however, control for many other factors, such as race, socio-economic status, parents' educational level, and even earlier academic success. Marsh and Kleitman controlled for dozens of such factors, and still found a significant -- though small -- positive correlation between athletic participation and academic achievement.
Achievement can be measured in many ways -- grades, homework, attendance, standardized test scores, and enrollment in college. In all of these areas except standardized test scores, even after controlling for economic status, race, and other background variables, athletic participation was significantly correlated to academic achievement.