The purpose of this monograph is to stimulate discussion of vertical equity through an assessment of the funding systems in four states (California, New York, Texas, and Wisconsin) that ascertains how and to what extent at-risk factors are addressed. (In education, children defined as at risk of low academic achievement or of dropping out represent the operationalization of vertical equity.) The paper is divided into six major sections, beginning with a description of the framework for analysis. This is followed by a description of the data and methods used in the study; an overview of the four states' school-funding systems; a description of at-risk funding in each state; and a cross-state comparison analysis. The at-risk funding factors included in the analysis are disability, poverty, urbanicity, race, limited English proficiency, and parental educational attainment. The paper closes with conclusions, policy implications, and recommendations for further research. Included are four tables describing incidence of students with at-risk factors for 1998-99; funding for at-risk factors in the four states school-funding systems for 1998-99; funding program for at-risk factors for each of the four states; and other funding program for at-risk factors for each of the four states. (WFA)