Data from Hong Kong PISA 2003 show that 15-year-old Hong Kong students who have immigrant parents from mainland China are grossly overrepresented in grades below the modal grade attended by most native Hong Kong students. Same-age comparison, when grade level is not taken into account, puts immigrants' children at a disadvantaged position in the mathematics, reading, and science literacy tests. The academic advantage of immigrants' children in Hong Kong is only revealed after grade is statistically controlled. Also, mainland immigrant students who are repeaters outperform native Hong Kong repeaters. Immigrant redshirting is a possible driving force behind these results. (Contains 5 tables and 10 notes.)