Purpose: This study investigates how the practice of dividing students and coursework into leveled categories persists in science education despite decades of efforts aimed at reducing inequities. This study makes underlying logics visible through an empirical analysis of how science educators attempt to reconcile an egalitarian vision of science for all students with divisive practices of grouping students and coursework into levels. Research Methods/Approach: This case study uses ethnographic methods during a 2-year period where researchers were embedded alongside teachers to investigate how a high school science department recreated hidden systems of leveled science coursework within a detracked institutional context. Data analysis draws on scholarship from Science and Technology Studies as well as organizational theory to examine how leveled categories are made through instructional logics built into teachers' work practice. Findings: Findings describe how certain students and science courses are categorized as "not honors material" through recursive discourses and practices that sort, divide, delay, and ultimately deny educational opportunities. Science teachers' instructional decision making was governed by two instructional logics: a mismatch logic and a not-yet-ready logic. These logics made it possible to enact stratification practices denying education opportunities to students seen as mismatched or unready for certain science coursework even as overt tracks were eliminated. Implications: Findings raise implications for current science education reform efforts aiming for greater equity, suggesting that categorization of science courses and students is entrenched in teachers' work practice and will need direct attention to dismantle.