Blue Skies Above the Horizon

In this commentary chapter, we draw on ideas from Baldinger and Murray; Cuoco; Wasserman and Galarza; and Zazkis and Marmur to articulate our views on the importance of mathematical structure and its relevance in secondary mathematics teachers’ disciplinary knowledge. In particular, we organize our discussion around two related questions—about the connections between abstract algebra and secondary school mathematics, and about how these connections can support the development of teachers’ disciplinary knowledge.