This is volume I of a two-volume study of the constitutionality of the K-12 funding system in Illinois. In this volume, seven steps are presented in the issues and outcomes of the major judicial challenges to systems of state aid to public schools. The first chapter looks at the history of state aid litigation up to the time California became the first state to experience a successful challenge to a state's system of aid to public schools. The second and third chapters analyze the California experience and what occurred between "Serrano vs. Priest" and "Rodriguez vs. San Antonio Independent School District." In the fourth chapter, the only decision on this issue that has ever been issued by the U.S. Supreme Court is considered. Chapters 5 and 6 review state court decisions on this issue, with chapter 5 looking at the litigation that upheld state aid systems and chapter 6 concentrating on those cases that overturned such systems. Chapter 7 considers the constitutional and statutory background related to the Illinois system of financing public schools and considers judicial actions originating in Illinois that have, in varying degrees, challenged some aspect of the Illinois system. This chapter also identifies fundamental questions, issues, and facts that tend to support or call into question the constitutionality of the present Illinois system. Case citations and references are included. (TE)