Check out the demographic pressures at play:

Wake County is relaxing its nationally recognized student diversity policy because its schools are having a harder time meeting the program’s goals.

School leaders plan to raise the ceiling for the percentage of low-income students at each school from 40 percent to 50 percent. Overnight, more than two dozen schools which were out of compliance with the district’s policy will be OK under the new policy.

The diversity policy, which has been held up as a national model, is based on the premise that schools with a diverse population perform better. … Wake is the largest district in the nation to strive for diversity based on family income. The district has been singled out by the U.S. Education Department as a role model for integration. Wake regularly receives visitors from around the country and internationally to see how the diversity policy is used. As recently as last week, a newspaper reporter from the Netherlands came to Wake to learn about the program.

But Wake has found it increasingly hard to keep schools diverse as the district has experienced record growth. Wake has picked up more than 29,000 students in the past five years. Many of those new students are poor.

No magic wand here. The district will always reflect the local population.