Most research on psychosocial consequences of neurofibromatosis type 1 (NF1) has focused on the relationship between disease factors and cognitive functioning. NF1 may impair domains of learning and attention, resulting in low academic performance. This study is the first nationwide population-based cohort study to investigate educational attainment and delay in completing mandatory school by persons with NF1. Educational information was collected from 550 persons at the age of 30 (born 1965–1984). They were diagnosed with NF1 in Denmark and compared to a cohort of NF1-free persons matched on gender and age (n = 4295). Multinomial logistic models were applied to estimate odds ratios (ORs) for obtaining short (≤9 years) or medium (10–12 years) education compared to long education (>12 years) by the age of 30 years. We calculated the probability of graduating 9th year of mandatory school at different ages in 932 persons with NF1 and 7962 NF1-free persons (born 1965–2000) using quantile regression. The OR of educational completion for short- and medium-term education was three fold (95% CI 2.55–3.99) and 1.29 fold (95% CI 0.99–1.69) higher, respectively, for persons with NF1 than NF1-free persons after adjusting for birth year, gender, psychiatric and somatic morbidity and mother’s education. Persons with NF1 were significantly delayed in graduating mandatory school education compared to NF1-free persons. When 90% of persons have graduated, persons with NF1 were 1.2 times older than the NF1-free persons. Experiencing delays in mandatory school likely affect further educational achievements and may impair employment and entering work force.