Early school entry and acceleration as means of catering for academically able students continue to attract advocates as well as critics. In this paper data from the large Australian Mathematics Competition (AMC) are used to examine the performance in mathematics of students young for their grade. The youngest students generally performed well above average on the AMC papers; the oldest group typically achieved substantially below the grade mean. There were proportionately more males than females in the older group but no gender differences were noted in the composition of the younger group. Items common to papers attempted by students at four grade levels fell into two clusters: questions which were challenging for the majority of students but consistently easy for the best students, and questions which were distinctly difficult for the majority of students but apparently suitable for the best mathematics students. As in other timed mathematics competitions, gender differences in performance were found.