Most of the studies of the return on investment in early childhood education have focused on the big payoffs in reduced public and societal costs associated with child welfare, public assistance, crime and incarceration, and benefits related to increased education and earnings. Several studies focus specifically on costs and benefits within the K-12 system, primarily measuring the effects of early childhood interventions on special education spending. This cost-benefit study focuses on the financial costs within the Minnesota K-12 system as a whole due to children entering kindergarten unprepared for school success. The study scope does not include costs or benefits for the child, family, or society. This study found the estimated cost burden to the Minnesota K-12 system due to children entering kindergarten unprepared for school success is about $113 million annually. An appendix containing tables and figures is included. (Contains 14 figures.) [This paper was prepared for the Bush Foundation. For the summary, see ED511611.]