The landscape of developmental education has experienced significant shifts over the last decade nationwide, as more than 20 states and higher education systems have transitioned from the traditional prerequisite model to corequisite remediation. Drawing on administrative data from Tennessee community colleges from 2010 to 2020, this study examined the heterogeneous effects of corequisite reform for remediation-eligible students with varying levels of academic preparation. Using difference-in-differences and event study designs, we found that corequisite remediation significantly improved gateway and subsequent college-level course completion for students in all placement test score groups below the college-level threshold. For math, the positive effects on college-level course completion were stronger for higher-scoring remedial students than for those with lower placement test scores, whereas the pattern was reversed for English. However, since the corequisite reform, students requiring remediation were more likely to drop out of the public college system, and those with the lowest scores were less likely to earn short-term certificates.