Children from families of low socioeconomic status (SES) tend to experience lower academic achievement than children from middle-SES families. This discrepancy can be attributed to a range of parental factors. The present study tested: (1) the extent to which academic achievement in three core subjects differs between children from low- and middle-SES backgrounds; (2) the differences in parental expectation, parental involvement, and child engagement across the two groups; and (3) the mediating role of parental expectation, parental involvement, and child engagement in explaining how SES influences children's academic achievement. The sample consisted of 184 primary students with low SES and 165 primary students with middle SES from mainstream primary schools in Hong Kong. Results revealed significant differences in parental expectation, parental involvement, child engagement, as well as academic achievement in Chinese and English subjects between the low-SES and middle-SES groups. Our findings also suggest that parental expectation, parental involvement, and child engagement may be important mediators in the relationship between SES and academic achievement. Copyright © 2020 Elsevier Ltd. All rights reserved.