A longitudinal daily diary method was employed to examine the implications of family assistance for the academic achievement of 563 adolescents (53% female) from Mexican (n = 217), Chinese (n = 206), and European (n = 140) backgrounds during the high school years (mean age 14.9 years in 9th grade to 17.8 years in 12th grade). Although changes in family assistance time within individual adolescents were not associated with simultaneous changes in their Grade Point Averages (GPAs), increases in the proportion of days spent helping the family were linked to declines in the GPAs of students from Mexican and Chinese backgrounds. The negative implications of spending more days helping the family among these two groups was not explained by family background factors or changes in study time or school problems. These results suggest that the chronicity rather than the amount of family assistance may be difficult for adolescents from Mexican and Chinese backgrounds.