Background Differential Susceptibility Theory (DST) postulates that some children are more affected - for better and for worse - by developmental experiences, including parenting, than others. Low birth weight (LBW, 1,500-2,499 g) may not only be a predictor for neurodevelopmental impairment but also a marker for prenatally programmed susceptibility. The aim was to test if effects of sensitive parenting on LBW and very LBW (VLBW, <1,500 g) versus normal birth weight (NBW, ≥2,500 g) children's academic achievement are best explained by a differential susceptibility versus diathesis-stress model of person-X-environment interaction. Methods Nine hundred and twenty-two children ranging from 600 g to 5,140 g birth weight were studied as part of a prospective, geographically defined, longitudinal investigation of neonatal at-risk children in South Germany (Bavarian Longitudinal Study). Sensitive parenting during a structured mother-child interaction task was observed and rated at age 6 years. Academic achievement was assessed with standardized mathematic, reading, and spelling/writing tests at age 8 years. Results Maternal sensitivity positively predicted the academic achievement of both LBW (n = 283) and VLBW (n = 202) children. Confirmatory-comparative and model-fitting analysis (testing LBW vs. NBW and VLBW vs. NBW) indicated that LBW and VLBW children were more susceptible than NBW to the adverse effects of low-sensitive, but not beneficial effects of high-sensitive parenting. Conclusions Findings proved more consistent with the diathesis stress than differential-susceptibility model of person-X-environment interaction: LBW and VLBW children's exposure to positive parenting predicted catch-up to their NBW peers, whereas exposure to negative parenting predicted much poorer functioning.