Education plays a crucial role in the development and consolidation of equality in society, which is reflected in the SDGs of the UN 2030 Agenda. Knowing the educational performance of schools is necessary to diagnose needs, evaluate proposals and undertake improvements in education policies. This study pursued a twofold objective: (1) to assess the equity and parity of Andalusian schools in relation to the competencies of mathematical reasoning and linguistic communication and (2) to study the relationship among educational performance, equity and parity in these competences. Hierarchical linear model research was designed and implemented in a population of 79,806 schoolchildren and 2092 schools. The results confirmed differences in equity and parity among schools. A relation was found between higher effectiveness and higher parity. Nonpublic schools are not more efficient than public schools; rather, it is the average economic and sociocultural status of schools that controls for their effectiveness. In conclusion, the educational system does not guarantee the same opportunities for all children; thus, the equity and parity of educational systems should be key criteria for their evaluation, ensuring that quality education reaches everyone equally. Further implications are also discussed.