This study examined quality assurance in the implementation of Universal Basic Education (UBE) in junior secondary schools in Bwari Area Council, Federal Capital Territory, Nigeria. The UBE programme has promised nine years of free, compulsory, and quality basic education since 2004, yet classroom outcomes tell a different story. Three research questions and three corresponding null hypotheses guided the inquiry, centred on teacher qualification and welfare, infrastructure and the learning environment, and curriculum and instructional materials, and on how each of these related to the effectiveness of UBE implementation. A correlational survey design was adopted. A structured questionnaire, validated by experts in educational management and scored on a four-point scale, was administered to 250 respondents comprising principals, teachers, students, and UBEC staff in Bwari Area Council, selected through stratified random sampling. Cronbach's alpha for the instrument's clusters ranged from 0.71 to 0.88. Data were analysed using frequency counts, percentages, means, and multiple regression. The results indicated that quality assurance was weak across all three indices, with infrastructure showing the strongest association with implementation effectiveness (β = 0.41, p < .001), followed by teacher welfare (β = 0.33, p = .002) and curriculum materials (β = 0.19, p = .041). The three predictors jointly accounted for 38% of the variance in implementation outcomes (R² = 0.38, F(3, 246) = 50.12, p < .001). The study concludes that UBE in Bwari Area Council operates without a functioning quality assurance framework, and recommends sustained budgetary release for quality assurance activities, infrastructure rehabilitation led by the FCT Administration, and closer monitoring by UBEC and the FCT Universal Basic Education Board.