Looking through the lens of our cohort's success in 9th grade.
We use 9th-grade students' promotion to the 10th grade, on schedule, as a measure of how well the middle-school years set students up for early high-school success. Our cohort includes Rhode Island's public-school 6th-graders in SY2007-08. Four years later our cohort either completed 9th grade, or they did not.
By the 10th grade our cohort has split into two groups:

began 9th grade on schedule but either stayed back or dropped out.
DATA NOTE: In K-8 students who fail repeat the entire grade. In high school, students may be promoted even if they fail one or more courses. Consequently, some of our official "completers" may have failed a course or more.