We share results from a one-year early algebra classroom intervention. One kindergarten, one first-grade, and one second-grade classroom participated in the intervention and three classrooms of the same grade levels served as control sites. The intervention addressed the structure of even and odd numbers, mathematical equivalence and equations, properties of arithmetic, the representation of varying unknown quantities, and functional thinking. Students in the control classrooms received their regular mathematics instruction. We compare growth in algebraic thinking across the two groups as measured by an online assessment completed by 40 students per condition. Findings suggest that students who participated in the early algebra lessons experienced more overall growth in their understanding of early algebra concepts as compared to control students.