The Phi Delta Kappa Study of Students At Risk assessed who is at risk, what puts students at risk, what schools are doing to help those students, and how effective these efforts are. Data were provided on at-risk students in 85 U.S. and Canadian communities by teachers who knew each student best and had access to a student's school records. This document describes the study and efforts to validate a scale for use in predicting risk among young people. It displays data on 21,706 students in 99 tables and 170 graphs, most of which are incorporated in 11 appendixes. Some data are included about how the 276 study schools were selected and how data about students were collected. Chapters describe previous reports of the study and the analysis approach; an attempt to assess risk among young people and to predict instances of further risk over a 2-year period; and a framework for interpreting data collected about young people in the 276 study schools. Appendixes, which comprise the major part of the document, include detailed instructions that researchers used to identify study schools; instruments used to collect information about principals, teachers, and students; an instrument used to collect follow-up information about 739 students 2 years later; an experimental version of a risk scale; and supportive statistical data. (RLC)