This study aimed to test three homework models defined in different cultures on Turkish high school students. HLM analyses were conducted on data collected from 1,229 high school students, considering 19 student-level and 7 grade-level variables. The dependent variables of the study were academic achievement and homework completion. The findings indicate that both variables exert a positive influence on one another. The influence of teacher and parental practices on academic achievement and homework completion in high school students is limited. Respect and support for student autonomy have been demonstrated to have a positive effect on academic achievement. Although motivation is a primary factor in academic achievement, effort and motivation are more influential in determining homework completion. When students demonstrate interest and perceive value in an assignment, they are more likely to exert greater effort to complete it. The perception of self-efficacy in relation to homework tasks has been found to have a positive effect on academic achievement and a negative effect on homework completion. The influence of educated parents on academic achievement and homework completion is contradictory. As students age, their academic achievement remains consistent, whereas their rate of homework completion declines.