To assess the association between abnormal timing of menarche among adolescent girls and neighbourhood socioeconomic status of their school area. Our analysis included 187,024 girls aged 15-18 years from the Korea Youth Risk Behaviour Web-Based Survey (KYRBS) from 2007 to 2015. Early and late menarche were defined as menarche before 11 years and no menarche by age 14 years, respectively. The deprivation index values for the areas where the schools were located were used as an indicator of neighbourhood socioeconomic status based on the 2005 national census data. We calculated odds ratios (OR) for early and late menarche using a multinomial logistic regression model. Covariates included body mass index, parental education, single or stepparents, siblings, household wealth, year of birth, survey year, and urbanisation. Mean age at menarche was 12 years. The overall proportions of early and late menarche were 11.3% and 3.3%, respectively. When divided into four quartile groups based on the socioeconomic deprivation index, 11.3% of girls in the most deprived quartile and 10.6% in the least deprived area showed early menarche. The prevalence of late menarche did not differ across the deprivation index quartiles of school area. Attendance at schools located in highly deprived areas was associated with up to 10% higher risk of early menarche. This positive association was not evident for late menarche. Among contemporary Korean girls, socioeconomic deprivation of the school area was associated with earlier puberty. This finding highlights the potential role of the socioeconomic environment of schools in women's lifetime health.