The present study investigated the relationship between child poverty and educational achievement among elementary (n=1,217) and middle school students (n=988) in South Korea using secondary data collected over a 12-year period (from 2006 to 2018) by the Korean Welfare Panel Study. This study used panel data to compare the impact of poverty on educational achievement for primary school students with secondary school students after controlling for self-esteem and three covariates (gender, bullying, and child maltreatment). The research examined the role of elementary and middle school students' self-esteem in mediating the relationship between child poverty and educational achievement. Using cohort data it investigated the effects of child poverty and self-esteem on students' academic achievement have changed over the past decades: 2000s (n=1,356) and 2010s (n=849).The study formulated six hypotheses based on a new model, SEED [Self-esteem, Economic status, Educational achievement, and Developmental status], which combines four theoretical backgrounds: the household production function [HPF] model (Becker, 1965), social causation theory (Dohrenwend & Dohrenwend 1969), the resilience framework (Rutter, 1987; Gilligan 2000), and a developmental perspective (Erickson, 1950; Kegan, 1982, Marcia, 1966; Piaget, 1963).The results of the study supported most of the hypotheses. Child poverty was a significant predictor of lower educational achievement, including academic achievement and school adjustment, among Korean elementary and middle school students. Self-esteem mediated the relationship between child poverty and educational achievement. The effects of poverty and the mediating effect of self-esteem differed by developmental stage and changed over the past decades. This study presents some implications for social work practice in schools and social policy and directions for future research to further understand the impact of child poverty and self-esteem on school achievement. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]