Rapid enrolment growth in Tanzania’s urban public secondary schools has enlarged classes, intensified teacher workloads, and strained instructional supervision. The study aimed to identify strategies used by administrators to enhance classroom-supervision quality in Ilala Municipality. It sought context-specific evidence to strengthen supervisory practice in expanding urban secondary schools. The dissertation adopted a qualitative approach and descriptive design, integrating questionnaire summaries with interview and observation evidence. The overall sample comprised 172 participants drawn from four public secondary schools: four heads of school, four academic teachers, four class coordinators, four class teachers, and 160 students; the objective-specific questionnaire table reported responses from 100 teachers. Simple random and purposive sampling procedures selected participants from four public secondary schools. Data were collected using structured five-point Likert questionnaires, semi-structured interviews, and an observation checklist. After clearances, the researcher administered questionnaires, conducted private interviews, and recorded observations during three months of school visits. Questionnaire data were analysed in SPSS version 26 using frequencies, percentages, and means, while interview and observation data underwent thematic analysis and triangulation. Content and construct validity were supported through objective alignment, review by two experts, and piloting outside the study schools. Questionnaire reliability reached Cronbach’s alpha = .70; standardized protocols, independent coding, and record keeping strengthened qualitative dependability. Ethical safeguards included informed consent, voluntary participation, confidentiality, anonymity, secure data handling, non-maleficence, and formal clearance. Findings showed strong endorsement of alternative supervision strategies and professional support (both M = 4.14), departmental meetings (M = 4.11), peer observation (M = 4.09), and continued effectiveness despite large enrolments (M = 4.05). Interviews and records confirmed mentoring, collaborative observation, scheduled follow-up, and departmental problem-solving. The study concludes that distributed, developmental supervision can preserve instructional oversight under enrolment pressure. It recommends institutionalized peer observation, protected departmental review time, documented feedback, supervisor training, and additional staffing and resources.