Research has found a relation between motivation and attributions for success and failure. However, few studies have clarified the relationship of attributions to school achievement and possible cultural differences in this relationship. To investigate this issue, 5333 secondary students (European, Asian, Maori, Pacific) rated four common attributions--ability, effort, task difficulty, and luck--and three social influences (teachers, peers, and family) for their best and worst marks. Motivation orientations were also measured. Several measures were significantly related to students' GPA scores, most notably the motivation orientations "Doing My Best" and "Doing Just Enough", but also attributions to effort, teacher, and peer influences. There were substantial differences for ethnicity, particularly between European students and Maori and Pacific students. The results support theories claiming that effort attributions motivate achievement but also support the benefits of a self-serving bias.