This article investigates children's elementary school experiences, exploring how they become autonomous, rational individuals--the type of person envisioned in the European Enlightenment and generally imagined as the outcome of Western schooling. Drawing on ethnographic research that followed one cohort of Latinx children across five years, we examine how schooling practices change across the elementary school years in a context that foregrounds high-stakes testing. We describe how practices that focus heavily on testing mold children into autonomous, rational individuals while marginalizing those who don't fit this model. Adhering to these practices and naturalizing the Enlightenment subject limits educators' ability to serve students who resist the normative practices of schooling.