This research investigated the question: What insights can be gained from autoethnographic exploration of my experiences with reform-based science education systems in Canada, England, and the United States? Autoethnographic data was collected from recollections of my experiences teaching, researching, and leading in secondary science education over a decade (2012-2023) in three countries (Canada, England, and the United States), and presented for this research as narrative vignettes. In response to calls to capture the interplay between stakeholders and infrastructure, and to better understand and document the ways in which educational systems enact policy, I used a layered approach to analytic autoethnography to explore my experiences implementing and enacting reform-based science education. Analysis of my narrative vignettes led me to identify similarities and differences from my experiences across national and professional cultures. I discovered that while some context-dependent differences existed, robust enactment of science education across all three experiences was hindered to varying degrees regardless of infrastructural or cultural nuances. From a positioning of inbetween, I was able to capture unique insights into the innerworkings, tensions, and negotiations that took place in the third space between policy and practice from my lived experience. This research aims to increase visibility for internal intermediaries positioned in the inbetween of science education systems and to highlight autoethnography as a reliable science education research method for providing insight into the everyday ‘what is’ of science education systems in contrast to the ‘what should be’ as outlined in the aims and goals of government educational policy documents.