This study evaluates the impacts of two mobile-phone-based distance education interventions, involving direct parental engagement, on parenting styles and children's cognitive development. Drawing from two randomised controlled trials conducted in rural Bangladesh during the Covid-19 pandemic, we examine two interventions: 1) Telementoring, where volunteers mentored mothers and tutored children over the phone; and 2) IVR Audio-lessons, where mothers accessed pre-recorded audio lessons for their children via a toll-free number. The Telementoring program significantly increased mothers’ authoritative parenting scores by 0.53 SD, while the IVR Audio-lesson program led to a 0.24 SD increase. Mediation analyses suggest that changes in parenting style accounted for 0.03 SD and 0.04 SD increase in children's test scores, or mediated 4 % and 8 % of the total intervention effect on children's test scores for Telementoring and IVR Audio-lessons, respectively. The findings underscore the potential of scalable and cost-effective phone-based interventions to enhance parental roles and foster children's human capital development in low-resource settings.