We present a research mathematician's perspective on current developments around in K-12 mathematics. We share activities, and highlight the different ways in which students' reasoning can progress, such as amount of abstraction, sophistication of representation, amount of autonomy and use of language. We end with recommendations for college and university faculty to support greater development of student reasoning in K-12.

5 pages, 2 figures; provisionally accepted to the Notices of the American Mathematical Society