The purpose of this longitudinal study was to examine patterns in implementation of Tier 2 and 3 school-wide positive behavioral interventions and supports (SWPBIS) systems to identify timings of installation that led to higher implementation of advanced tiers. Extant data from 776 schools in 27 states reporting on the first three years of Tier 2 implementation and 359 schools in 23 states reporting on the first year of Tier 3 implementation were analyzed. Using structural equation modeling, we found that higher Tier 1 implementation predicted subsequent Tier 2 and Tier 3 implementation. In addition, waiting two or three years after initial Tier 1 implementation to launch Tier 2 systems predicted hither initial Tier 2 implementation (compared to implementing the next year). Last, we found that launching Tier 3 systems after Tier 2 systems, compared to launching both tiers simultaneously, predicted higher Tier 2 implementation in the second and third year, so long as Tier 3 systems were launched within three years of Tier 2 systems. These findings provide empirical guidance for when to launch Tier 2 and 3 systems; however, we emphasize that delays in launching advanced systems should not equate to delays in more intensive supports for students. [This paper will be published in "Journal of Positive Behavior Interventions."]