This study examined disparities in learning outcomes attributable to the implementation of the Competency-Based Curriculum (CBC) assessment reform across urban and rural primary schools. Guided by a comparative cross- sectional design, the study was informed by human capital and equity-in-education frameworks and sought to establish the extent to which school locality, teacher CBC training, school resourcing, socioeconomic status, and parental involvement predicted learners' attainment of competency proficiency. A structured assessment and school- characteristics questionnaire was administered to a sample of 700 upper-primary learners and their corresponding class teachers drawn from purposively selected urban (n=320) and rural (n=380) schools, using a multistage stratified random sampling procedure. Data were analysed in Stata using univariate frequency distributions, bivariate chi-square tests of association and independent-samples t-tests/one-way ANOVA, and a multivariable binary logistic regression model to identify independent predictors of competency proficiency while controlling for confounding. Findings indicated a substantial urban-rural gap in mean CBC assessment scores (84.7% versus 66.2%, p<0.001) and in the proportion of learners attaining proficiency (99.1% versus 69.2%, p<0.001). Bivariate analysis confirmed significant associations between locality and teacher training status, socioeconomic status, and parental involvement (all p<0.001). In the adjusted multivariable model, teacher CBC training (AOR=5.77, 95% CI: 3.13-10.62), school resource index (AOR=1.49, 95% CI: 1.26-1.76), high socioeconomic status (AOR=16.12, 95% CI: 4.87-53.33), and parental involvement (AOR ranging 7.23-7.93) emerged as independent predictors of proficiency, whereas urban locality itself was attenuated to marginal significance (AOR=3.55, 95% CI: 0.89-14.15, p=0.072) once these structural factors were controlled for, and larger class size independently reduced the odds of proficiency (AOR=0.95, p=0.001). The study concludes that urban-rural learning outcome disparities under CBC are substantially mediated by inequities in teacher training, school resourcing, class size, and household-level socioeconomic and parental support factors