When first elected in 1989, Daley eagerly reached out to those in the city's predominantly white professional class. They were edgy and many were considering leaving Chicago.
In response, the mayor built top magnet and college prep high schools, pushing through work-rule changes to attract the best teachers. He produced the schools that nervous white-collar voters demanded.
Members of the professional class wanted city life. But they wanted their children educated. They became clients of Daley's first tier. (emphasis added)
This is almost never mentioned, but the effect of switching from seniority to "mutual consent" ("criterion-based hiring," etc.) is more efficient sorting of the best teachers into the most desirable schools. Otherwise grumpy senior teachers can grab the spots in what are supposed to be the "good schools."