Kindergartners' base-10 knowledge predicts arithmetic accuracy concurrently and longitudinally

Children's early knowledge of the base-10 structure of multi-digit numbers has been hypothesized to play a critical role in subsequent learning of mathematics, in particular arithmetic operations. The present study investigated the relation between base-10/place value understanding and arithmetic accuracy in early elementary school. Children were assessed in kindergarten (N = 90) and then a subgroup of participants was assessed again two years later in second grade (N = 21). Mediation analyses indicated that, in kindergarten, base-10 knowledge had a direct effect on arithmetic accuracy as well as an indirect effect through the use of a decomposition strategy. Furthermore, kindergarten base-10 knowledge had a direct effect on arithmetic accuracy in second grade and an indirect effect through second grade place-value notation understanding. Implications for understanding early mathematical development are discussed.