An alternative mathematics preparation program for K-8 teachers is described as an existence proof that steadily increasing effectiveness of STEM (science, technology, engineering, and mathematics) preparation is possible. The program is based on treating every lesson in each of five mathematics content and methods courses as objects of study. Increasing performance from cohort to cohort of K-8 preservice teachers of mathematics-for-teaching tasks is explained by the increasing knowledge acquired over time for helping preservice teachers achieve lesson-level learning goals. Arguments are offered for the potential of this kind of program to strengthen, in a lasting way, the STEM education of preservice teachers and their motivation to study and improve their own teaching practice over time.