This study aimed to explore students’ perceptions of school practices that have ethical significance using an integrative model based on the eighth-grade Trends in International Mathematics and Science Study (TIMSS) 2015. The sample comprised 280,130 students, 8,353 principals, and 8,353 teachers from 8,353 different schools across 45 countries. Based on Mplus V.8.0 analyses, the results show that ethical school practices fall into three main categories: caring about students’ learning, student bullying, and sense of belonging. These findings expand on the meaning of ethical school practices beyond the concept’s original definition, and suggest that the original items of the TIMSS student questionnaire contain unmined potential. The findings encourage an integrative approach, including ethical school practices and intra- and extra-school factors, to exploring the factors that relate to student achievement. In addition, this study has produced a new multinational index that can help explain similarities and differences among countries.