A follow-up of a cluster-randomized trial evaluated the long-term impacts of a scale-up model composed of 10 research-based guidelines grounded in learning trajectories. Two treatment groups received the intervention during the prekindergarten year, and one of these groups received follow-through support in kindergarten and first grade. Business-as-usual curricula were used in all other cases, including all years for the control group. Early effects on mathematics achievement decreased through fourth grade but reemerged at fifth grade. These results support both a latent trait hypothesis, whereby stable characteristics of students explain differences in achievement, and a latent foundation hypothesis, whereby early mathematical knowledge and skills provide a foundation for competence in mathematics in later years, especially those that involve challenging mathematics.