This study examined the relationship between family educational level and students’ academic performance in selected public secondary schools in Nigeria. Anchored on Coleman’s Social Capital Theory, the study adopted a cross-sectional survey design involving 255 Senior Secondary Two (SS2) students drawn from Lagos, Oyo, Kano, Rivers, Enugu and the Federal Capital Territory. Family educational characteristics were measured through father’s education, mother’s education, combined family educational level, parental involvement, home-learning conditions and parental expectations, while family income and private tutoring were treated as relevant covariates. Academic outcomes comprised overall academic score, grade classification, English Language score, Mathematics score and study motivation. Descriptive statistics, correlation analysis and multivariable regression were specified for the analysis. Preliminary analysis of the first 128 observations showed a pronounced educational gradient: students from low, medium and high family educational backgrounds recorded mean academic scores of 36.1%, 64.1% and 84.7%, respectively, while distinction rates were 0.0%, 5.6% and 100.0%. Family educational level was strongly correlated with academic score (r = .91), and maternal education showed a slightly stronger pattern than paternal education. Inspection of the complete dataset maintained the same directional pattern across academic score, English, Mathematics and study motivation. The study concludes that family educational level is strongly associated with students’ academic outcomes within the sampled schools and that this relationship occurs within a broader constellation of parental involvement, expectations, home-learning resources and socioeconomic support. The study recommends integrated school-family engagement, targeted support for disadvantaged students, equitable learning resources and further longitudinal research.`