If I were fascinated with the study of the health system in inner-city schools in America, and wanted to get a PhD to study how elementary school students were taught about their bodies in ways that perpetuated patterns of inequality, I would be interested in what sub-discipline of Anthropology?
It's cultural anthropology because you're interested in inequality patterns perpetuated by certain education, that's a cultural fact, it's not biological research, nor linguistic, nor archaeological.