Programs that connect higher and K-12 education provide benefits to K-12 students, teachers, and higher education. The National Science Foundation (NSF) invested in programs connecting domestic STEM graduate students with K-12 education for over a decade (GK-12), intending that such engagement would help achieve graduate student learning outcomes and would be sustained after NSF funding. By comparing two cohorts of graduate and post-doctoral student participants in a sustained GK-12 we have begun longitudinal assessment of a program as it matures and diversifies by integrating non-STEM and international students. Qualitative analysis of participant journals shows that the sustained GK-12 has continuing impacts on graduate students' teaching, teamwork, and communication skills, and aids in shaping their future career plans. A new theme that emerged in the later cohort related to participants' changing perspectives on pedagogy and teaching as a part of faculty responsibilities. We encourage universities seeking to meet expanded graduate student learning outcomes to consider adopting/adapting the GK-12 model.