Internal locus of control (LOC) is a highly beneficial non-cognitive skill, yet its long-term formation process remains poorly understood. Using British cohort data, we examine the role that fathers play in LOC maturation from childhood into middle age; a machine-learning algorithm is used to identify the most common LOC maturation types. Estimating a standard skill production function, we find that father's, but not mother's, interest in their child's education at age 10, as assessed by the child's teacher, predicts internality in middle age for female and socioeconomically disadvantaged children. Father's interest increases the probability of lifelong internality by 20%, and protects against lifelong externality. Parental engagement in children's education is a malleable factor, and thus is a promising target for public policy.