A burgeoning literature has documented the influence of adjunct instructors on student subsequent interest and success, but very little is known about the underlying mechanisms. This study investigates instructor choice of grading standards as one mediating channel by exploiting a unique university policy that converts full-time permanent lecturers from existing pool of part-time temporary instructors. We find that instructors hired on a temporary, part-time basis assign higher grades than their permanent full-time counterparts, with no discernible differences in student learning outcomes or perceived teaching effectiveness. The differential grading standards, however, appear to have a nonnegligible impact on student enrollment patterns.