Preschool through third grade (P-3) alignment is regularly named as a key aspect of early childhood education and the transition to formal schooling. However, little is known about P-3 alignment in practice. Using data from 265 observations of math instruction in preschool, kindergarten, first-, and third-grade classrooms in New York City public schools, we explore P-3 instructional alignment as it would be experienced sequentially, over time and across grades, by students. We examine the continuity of developmentally appropriate instructional environments and high-quality pedagogical practices, as well as the progression of P-3 mathematics content coverage. We find notable discontinuities in instructional environments and some pedagogical practices, particularly across preschool and kindergarten. We also find both progression and repetition in math content coverage. Results suggest that, on some dimensions, kindergarten may be poorly aligned with both preschool and the early elementary grades.