Objectives: While Macao is considered one of the top ten economies in mathematics literacy for its 15-year-old students, the proportion of students who have repeated grades at the primary and secondary levels is amongst the highest amongst all PISA participating economies. Schools argued that it is because of the implementation of the grade repetition policy, which is a form of school-based accountability of minimum educational standards, that they are able to top the league table of mathematics literacy performance amongst participating economies. This study seeks to provide convincing research-based evidence to inform policy makers to make a proposal to abolish grade repetition policy in primary schools in Macao. Design/Methodology: In PISA2003 and PISA2012, mathematics performance of the 15-year-olds who have repeated or not repeated grades are compared. Results: Although student has repeated only once in the primary grades there is a statistical significant 1.7 grade level drop in mathematics performance. Within a decade, this performance drop increases further to 2.2 grade level, showing that the students suffer from the perils of grade repetition. Conclusion: Because of adverse effects cast on the primary/secondary students, Macao schools are urged to abolish the grade repetition policy for the common good of the society.