Despite the claim by several researchers that variability in performance may complicate the identification of "at-risk" children, variability in the academic performance of young children remains an undervalued area of research. The goal of this study is to examine the predictive validity for future scores and the score stability of two widely administered Dutch preschool tests. Specifically, the focus was on their suitability for identifying children that are at risk for academic difficulties. To evaluate at-risk identification using early standardized assessment, language and math scores were collected over a four-year period (N = 431). Score stability was evaluated by means of transition rates and score differences. Predictive validity was assessed using a mixed model. The majority of low-scoring children showed broad fluctuations in scores, although 12% to 17% did remain relatively stable in their scores. Correlations between preschool scores, and first- and second-grade language and math measurements were estimated at between 0.09 and 0.30. The longitudinal design of this study illustrates how assessment scores can fluctuate over time, which is a problem that may be inherent in this age group but one that warrants greater attention. This study provides a transparent evaluation of the suitability of assessments used for identifying children at risk for academic difficulties.