This study examined single parenthood and students’ lifestyle among selected public secondary school students in Nigeria using a comparative cross-sectional design. The study sample comprised 270 students drawn from Lagos, Oyo, Rivers, Enugu, the Federal Capital Territory, and Kano, with equal allocation to two-parent, single-mother, and single-father households. Outcomes included academic performance, disciplinary issues, substance use, peer influence, social behaviour, emotional well-being, and a composite lifestyle risk score, while parental supervision, parental education, and parental income were considered as relevant family and socioeconomic characteristics. Verified preliminary analysis of the first 135 observations showed marked unadjusted differences across family structures. Students from two-parent households recorded a mean academic score of 81.9%, a mean lifestyle risk score of 1.4, and 0% reported substance use, compared with 46.2%, 7.2, and 48.9%, respectively, among students from single-mother households, and 51.3%, 6.2, and 31.1% among students from single-father households. The descriptive pattern further suggested that stronger parental supervision accompanied more favourable academic, behavioural, social, and emotional outcomes. The study concludes that family structure is associated with multiple dimensions of student lifestyle, while parental supervision and socioeconomic circumstances are important accompanying factors. Because the design is cross-sectional, the findings should be interpreted as associations rather than causal effects.