This article examines how notions of health and citizenship have become entangled in US science education reforms targeting particular populations. Current science education policy assumes that marginalized groups have been historically ignored, and that new research is required to "make diversity visible" in order to adapt instruction for those students. This article questions that premise, asking instead how key practices of US science education emerged in response to the fabricated presence of racialized (non)citizens. Interweaving lines of inquiry from cultural studies and science & technology studies, I analyse a set of pedagogies that circulated across US science education, public health, and colonial projects in the early twentieth century. I explore how this pedagogical apparatus doubled as a strategy of governance, rendering citizenship into a biomedical status that had to be proven rather than assumed. Finally, I raise questions about recent reforms that hope to leverage public health concerns (e.g. obesity) to make science instruction more inclusive and culturally responsive. A danger is that efforts to respond to the needs of "diverse groups" may inadvertently reinscribe diversity as pathology. This can occur when reforms continue to rely on educational practices that mark exclusionary boundaries of biomedical citizenship.