Middle school data from the Third International Mathematics and Science Study (TIMSS) are analyzed in this article to compare achievement difference between seventh and eighth grades. The statistical computing involves a selective subtraction of item scores in more than 40 countries. The research findings indicate that not all TIMSS items have resulted in a higher mean score at the upper grade level. Item features are discussed to characterize part of the released TIMSS instrument that generates a higher average score at the lower grade. This empirical study may help enrich understanding of the TIMSS benchmark among mathematics and science educators.