This report is designed to provide a detailed picture of the relationship between students' performance in the middle grades (grades five through eight) and their subsequent performance in high school and college among students in the Chicago Public Schools (CPS). The key findings of this report have been summarized in briefs for middle grade and high school practitioners: 5 Key Findings for Middle Grades and 4 Key Findings for High Schools. Grades and attendance--not test scores--are the middle grade factors most strongly connected with both high school and college success. In fact, grades and attendance matter more than test scores, race, poverty, or other background characteristics for later academic success. This report follows approximately 20,000 Chicago Public Schools students as they transition from elementary to high school. It is designed to help answer questions about which markers should be used to gauge whether students are ready to succeed in high school and beyond. It also considers the performance levels students need to reach in middle school to have a reasonable chance of succeeding in high school. Key findings from the report include: Only those students who leave eighth grade with GPAs of at least 3.0 have a moderate chance of earning a 3.0 GPA in high school--the threshold for being considered college-bound. Whether students are "ready" for high school depends not only on their academic performance in the middle grades but also on the context that they enter into in ninth grade. Students with the same academic record in middle school also have different high school outcomes depending on which high school they attend. Strategies aimed at attendance improvement could likely have as much or more of a payoff for high school and college graduation as efforts aimed at improving test scores becausetest scores are hard to move and do not show much variability throughout middle and high school. Meanwhile, attendance shows considerably more variation and middle school attendance is much more predictive of passing high school classes than test scores.