The development of number line estimation in children at risk of mathematics learning difficulties: A longitudinal study

•Number line accuracy and estimation patterns were studied in children at risk of MLD.•Number line accuracy predicted growth in numerical operations and math reasoning.•Number line accuracy predicted intercept but not growth (slope) in math fluency.•Children best fit by the linear outperformed those best fit by the logarithmic model.•Math skills did not differ based on models from the proportion judgment perspective. Children with mathematics learning difficulties (MLD) show poorer performance on the number line task, but how performance on this task relates to other mathematical skills is unclear. This study examined the association between performance on the number line task and mathematical skills during the first 2 years of school for children at risk of MLD. Children (N = 100; Mage = 83.63 months) were assessed on four occasions on the number line task and other mathematical skills (math fluency, numerical operations, and mathematical reasoning). Estimation patterns were analyzed based on the representational shift and proportional judgment accounts separately. More consistent longitudinal trends and stronger evidence for differences in mathematical skills based on estimation patterns were found within the representational shift account. Latent growth curve models showed accuracy on the number line task as a predictor of growth in some mathematical skills assessed. We discuss impacts of methodological limitations on the study of estimation patterns.