This article aims to discuss whether external evaluations are instruments to ensure increased quality of public school education. It is part of a research that investigated how evaluation results and the resulting indices were used in two schools in the state of São Paulo (Brazil). The methodology adopted was the case study, using different methodological tools such as interviews (intended for school coordinators and supervisors), questionnaires (intended for teachers and school directors) and observation of pedagogical meeting schedules. The collected data were analyzed and contextualized from studies by authors such as Afonso (2009), Dale and Robertson (2006), Le Grand (1991) and Neave (1988), among others, who investigated the commodification of education and external evaluations. In conclusion, we noticed that the mere existence of an external evaluation, accompanied by an index, is not sufficient to ensure improved quality of education, as this is done with the participation of parents, a good initial teacher training and investment in their continued training and higher social investments in the communities. External evaluations, contrary to what they promise, have on many occasions enabled increased regulation, ranking and competition, but have decreased the autonomy of schools thereby, reinforcing school inequality.