In this study, we investigated how early numeracy skills develop in kindergarten-age children. The participants were 235 Finnish children (111 girls and 124 boys). At the time of the first measurement, the average age of the children was 6 years. The measurements were conducted three times during 1 year of kindergarten. We used a between-group repeated-measures analysis of variance and post hoc group comparisons for three measurement times on two related mathematical scales. The results showed that differences in mathematics skills among children are already visible in kindergarten before formal primary education in mathematics starts. The early numeracy skills measured, namely, relational skills in a numerical context and counting skills, were weaker over the kindergarten year in low-performing children, and, although their skills improved, they did not catch up to their average peers.

This article concerns psychometric aspects of the Finnish Early Numeracy Test, which has been translated from the original Dutch Early Numeracy Test. The advantage of the test is that young children's numerical skills can be assessed systematically, which was not possible previously in Finland. A norm study was conducted in which the test was administered to a representative sample of 1,029 Finnish children. The reliability and validity results justify the use of the test as an early-childhood screening test and in research on number sense. The indicative effects of gender, parental professional education, domicile and number of siblings are discussed.