The results of large-scale student assessments have provided information on the factors that may have an impact on both academic performance and educational equity in schools. Therefore, considering the results obtained in the TIMSS 2019 Program in Spain, two indicators of equity, as equality of results and as equality of opportunities, have been extracted and predictor variables of context and teacher professional development have been identified, studying their relationship with these indicators. In addition, considering the influence of the previous stages on the subsequent ones, it has been analyzed whether there is any kind of relationship between the factors that have an impact on the stages of compulsory education in Spain (primary education and compulsory secondary education). The results suggest that the variables socioeconomic and cultural status, training on improving students’ critical thinking or problem-solving skills, and need for training on integrating ICTs in mathematics’ instruction are highly related to the equity as equality of results criterion variable, and only the variable training on addressing individual students’ needs has a strong relationship to the equity as equality of opportunities criterion variable. Furthermore, there are not many similarities between the results obtained in TIMSS and PISA, except for the variable training on addressing individual students’ needs, which has been observed to correlate in PISA 2018 with equity as equality of results and equality of opportunities criterion variables, and in TIMSS 2019 with equity as equality of opportunities criterion variable.