The 2011 Trends in International Mathematics and Science Study shows average mathematics scores of U.S. fourth graders are lower than children in many Asian countries. There are questions about differences in mathematics skills at younger ages. This study examines differences in score growth for High-, Average-, and Low-performing children in two U.S. states and one city in China. The samples are not representative of site populations and are different in socioeconomic status (SES). Test of Early Mathematics Ability-3 (TEMA-3; Ginsburg & Baroody, 2003) scores were obtained at four time points from the longitudinal samples. Children in Shanghai had higher scores than children in Kentucky and Nebraska; the majority of children in Shanghai scored in the High group, whereas most children in Kentucky and Nebraska were in the Average group. The best fitting growth models were nonlinear and the growth patterns varied across samples. More research is needed to understand how classroom instruction, home environments, parenting, and SES impact growth of TEMA-3 scores.