Scaling up educational interventions in the STEM (Science, Technology, Engineering, and Mathematics) field is critical but under-researched. We review and draw implications from a series of studies investigating the long-range impact of an implementation of an early mathematics scale-up model based on learning trajectories. Lasting effectiveness includes persistence, sustainability, and diffusion. We conclude that persistence of the effects on individual children's trajectories of learning is difficult to achieve, and support for children must be maintained through elementary school. More positive and perhaps more important, implementation of the scale-up model showed impressive sustainability with teachers as it increased their use of intervention components and their fidelity to high-quality instruction. Also promising has been indications of diffusion.