The ability to read the Qur'an correctly is an essential dimension of character formation and religious moderation among pre-service teachers, as mandated by national education policy for teacher professional development. Prior studies on Qur'anic literacy have largely focused on instructional strategies and program interventions, leaving the association of secondary school background largely unexamined among pre-service teachers. This study examines the relationship between secondary school background, namely senior high school (SMA), vocational high school (SMK), Islamic senior high school (Madrasah Aliyah), and Islamic boarding school (Pondok Pesantren), and the Qur'anic reading competence of 855 students from the Faculty of Teacher Training and Education, Universitas Samudra, batch 2025. An explanatory sequential mixed-methods design combined descriptive statistics, cross-tabulation, chi-square test, and ordinal regression with qualitative interviews to elaborate the findings among low-competence students. Results show a significant association between school background and Qur'anic reading competence (chi-square = 93.220, df = 12, p < .001), though the relationship was weak (Cramer's V = .191). Ordinal regression confirmed a significant association (chi-square = 67.667, df = 3, p < .001; Nagelkerke R-squared = .081), with Islamic boarding school graduates consistently more likely to achieve higher competence levels. Qualitative findings revealed four explanatory themes: learning duration confined to elementary school, the absence of formal academic requirements except in boarding schools, reluctance to relearn basic reading at an adolescent age, and insufficient parental attention. These findings indicate that school background was significantly associated with Qur'anic reading competence, underscoring the need for differentiated, stigma-free remedial programs for pre-service teachers.