By the Numbers

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Median: 1,690 students

The number of students enrolled in the school as of September 30, 2005. Five years ago, a few oversize and struggling Chicago Public Schools (CPS) high schools were converted into confederations of smaller schools sharing one big building. Arne Duncan, the CEO of CPS, said at the outset of this conversion that the aim was to improve students' ability to learn. Among the converted schools were Orr, South Shore, and Chicago Vocational. In each building, no high school would have more than 125 students per grade; compare that with Chicago Vocational's traditional configuration, with more than 600 students per grade. By June 2005, CPS had 23 small schools within its roster of more than 100 high schools. (That does not include charter schools.)

Last year, a University of Chicago study indicated that the smaller schools were not helping students score higher on standardized tests, a key measure of student achievement. The smaller schools did show big improvement in other categories, with lower dropout rates and higher school attendance; Duncan told the Chicago Tribune that those steps were the first toward higher scores.

Median: 21.1

Many schools, school districts, and parents tout class size as an indicator of school quality. Although that connection has been widely debated, there is little doubt that smaller class size, even if it does not lead to higher test scores, creates a more comfortable setting for learning and allows greater opportunity for more direct interaction between students and teacher.

Among the 20 schools with the largest class sizes are four that demonstrate that large classes are not necessarily an obstacle to high student achievement. York High School in Elmhurst, Neuqua Valley in Naperville, Community High School North in Downers Grove, and Glenbard West in Glen Ellyn have average class sizes of more than 25 students; yet students there score significantly higher on their ACTs and Prairie State Achievement Examinations than those at other schools with big classes.

Median: 92.6 percent

A school calculates this figure by averaging its daily attendance figures over the span of the school year. More than just a strict accounting, it is also a measure of how much students want to be at the school. Of the 50 schools with the lowest attendance rates, 45 are in Chicago. That means that while CPS has about 40 percent of the region's high schools, it has 94 percent of the most poorly attended schools.