Girls and boys segregation in schools is definitive of a sex-based classification, and, thus, it must be supported by an "exceedingly persuasive justification" to pass constitutional muster. In light of this requisite standard, the legality of single-sex educational institutions depends on the accuracy of underlying assumptions and support. Accordingly, it is important to be aware that a majority of research used to advocate the benefits of single-sex education is cloaked in uncertainty. Specifically, proponents "who want to build a case for single-sex education usually draw on ... uncontrolled studies, small samples, and anecdotal evidence; the positive findings are repeated but are not analyzed". Alternatively, opponents of single-sex education are able to gather tangible support from observable patterns of pervasive gender inequality in other social contexts.