Learning at home with parents (e.g. homework supervision, preparing exams) is recommended as the most important aspect with regard to parental involvement in schooling, which directly improves students’ educational outcomes (e.g. achievement, self-regulated learning). However, research investigating quality of parental instruction (QPI) and its determinants is still scarce. According to self-determination theory, QPI is characterized by different kinds of parental instruction (PI), either in authoritative (autonomy-support, responsiveness) or authoritarian (control, structure) ways. Numerous studies reveal that authoritative PI is likely to foster students’ educational outcomes, whereas authoritarian PI seems to weaken them. Furthermore, differences in QPI can be seen as “unequal opportunities” to learn at home, which students may unequally obtain from their parents due to different family conditions. This paper aims to investigate determinants of QPI in Thai families for a better understanding of inequalities in students’ educational outcomes. The sample consists of 494 students and their parents recruited from 8 schools in Bangkok and Chonburi, Thailand. Research hypotheses are derived from the theoretical models of Hoover-Dempsey and Sandler (1995, 1997). To test the hypotheses, structural equation modeling is employed. The results are expected to confirm that most of the hypothesized determinant factors contribute to the good prediction of differences in QPI.