 As applied to educational opportunity, formal equality of opportunity requires the removal of formal obstacles, in the form of laws or entrance criteria for educational institutions, which refer to ascriptive characteristics. For instance, formal equality of opportunity is opposed to legally segregated schools whose admissions policy states that students be white, male or belong to a certain religion. This conception is likewise opposed to laws that endorse or require segregation in schools. The Brown decision is certainly consistent with at least formal equality of opportunity. At the same time, it is worth noting that formal equality of opportunity is at odds with the tolerant attitude many societies take toward schools and colleges that are segregated by sex and religion. One possible way in which these practices might be reconciled with formal equality of educational opportunity would be to argue that this principle applies only to public educational institutions and not private schools and colleges. Some people accept that formal equality of opportunity is a sufficient norm to guide the distribution of educational opportunities, but most political and moral philosophers accept it as necessary but not sufficient. A principle of non-discrimination leaves open whether and to what extent the state needs to provide the resources that are required for education, or how those resources should be distributed (see Gutmann 1999: 127ff). Since resources are necessary for education—whether in the form of books and materials, teachers, facilities, and so on—formal equality of opportunity is compatible with some children failing to actually receive an education. Formal equality of opportunity fails to provide effective equality of opportunity.