Over the past decade, Latin America has not witnessed an improvement in the academic performance of its students, as evidenced by the Comparative and Explanatory Regional Study (ERCE) from UNESCO Santiago, where only Brazil, Peru, and the Dominican Republic achieved significant progress. To comprehend this phenomenon, this research employs an Oaxaca-Blinder variance decomposition, analyzing the results of the TERCE 2013 and ERCE 2019 exams and their relationship with structural, institutional, individual, and school factors. The findings indicate that improvements should have been observed in the region, linked to the socioeconomic status of the school and family expectations, as well as increased efficiency in certain educational factors. Nevertheless, the potential for these enhanced results is entirely nullified by a widespread deterioration across the entire region in the constant associated with unobservable attributes. This deterioration is not related with any of the variables incorporated in this study for the comparative analysis of the two periods. The unobserved effect could be associated with institutional factors beyond the education systems and at the school level, beyond the scope of this study.