At the end of July in 2002, haven just been granted mayoral control of school, Mayor Michael Bloomberg turned to a business leader, Joel Klein, then the CEO of Bertelsmann, Inc., to run the nation's largest school system.

"I look forward to working with teachers, parents and the Panel on Educational Policy," Klein said at City Hall that day, "because everyone is part of the solutions we seek to the challenges we face."

Eight years later, Klein is preparing to step down to become an executive at News Corp. And the mayor has tapped another business leader—Hearst Magazine's Cathie Black—as his replacement.

During his time at the city Department of Education headquarters at the Tweed Courthouse behind City Hall, Klein has—as he predicted--faced challenges. He has answered with three reorganizations of the school system, a reduction of social promotion, a laser-like focus on standardized testing, grades for schools, ratings for teachers, the break-up of large high schools into smaller ones, the closure of failing schools and a devotion to the charter school concept.

In an administration that values statistical measurement, there are myriad ways to measure the impact of Klein's initiatives. Different numbers paint different pictures: High school graduation rates are up. But standardized test scores in lower grades—used to justify continued mayoral control and to fortify the mayor's two re-election campaigns—were shown earlier this year to have been drastically inflated.

A typical child who started in Kindergarten the year that Klein took over Tweed still hasn't reached ninth grade. A third-grader this year, taking the first crucial standardized test, won't graduate high school until 2020. So it might be years until Klein's legacy can be fully assessed. But here are some of the ways City Limits has covered his tenure:

A 'D' For Details: Should The City Release Teachers' Ratings?
Nov 9, 2010 As a businesswoman prepares to take over the city's schools, New York's teacher rating system—itself borrowed from the business world—stirs controversy.

State Education Test Scores Take Nosedive
July 28, 2010 Elementary and middle school students statewide scored far worse this year on their annual state math and English exams. For New York City, it was the first year-to-year decline in at least four years.

We Won 'Race To The Top' Money. Now What?
Aug. 30, 2010 One thing that is clear, and of concern to many advocates and educators, is that the money isn’t going to particular school-based programs.

Hard Math: Charter Schools Race For Space
June 10, 2010 The new charter school law ended months of political acrimony. But it didn't answer the question of where the new schools will find seats.