Children in out-of-home care persistently show poorer educational and developmental outcomes than their peers. This study investigates the effect of the comprehensive educational intervention, "LUKoP," in a randomized controlled trial, compared to treatment-as-usual (TAU). Outcome measures included reading and math abilities, IQ and executive function, learning skills, and psychosocial functioning. One hundred foster children (66% female) aged 6-14 (M = 10.5, SD = 2.1) from 80 regular schools participated in the study. We applied a fixed-effects regression analysis. Regardless of group allocation, the children demonstrated significant progress in cognitive development, including IQ (ES = 0.40, p < 0.001), verbal comprehension (ES = 0.29, p = 0.02), and perceptual reasoning (ES = 0.60, p < 0.001) over time. The children who received the LUKoP intervention also had a significant increase in word-reading speed (ES = 0.21, p = 0.02) and a significant additional gain in IQ (ES = 0.34, p = 0.02) and verbal comprehension (ES = 0.41, p = .03), compared to TAU. No significant effect was found on the other outcome measures for either the TAU group (ES range = - 0.13 to 0.47, p > 0.05) or the LUKoP group (ES range = - 0.15 to 0.42, p > 0.05). We found no compelling evidence that the LUKoP intervention gives overall benefit to academic achievement; however, LUKoP demonstrated a greater effect on cognitive abilities than TAU. The findings and future directions for educational interventions for children in out-of-home care are discussed.