Research has suggested that school type is related to adolescents' likelihood to attend college. Neal (1997) found that Catholic schooling significantly increases educational attainment among urban minorities, while fewer gains of Catholic schooling were found for urban and suburban whites. Zaff, et al. (2001) found that adolescents who attend Catholic schools are more likely to attend college than adolescents from public schools, after controlling for individual, demographic, and family processes factors. However, as stated before, it is important to note that studies trying to compare educational outcomes of students who attended Catholic or private schools to students attending public schools may not be able to control for selection factors; that is, unobservable characteristics about motivational levels of parents and adolescents who attend private schools, for which they likely pay tuition. Such unobservable differences may account for some of the effects attributed to Catholic schools.