Why is the black and white student population decling in Maryland?

Okay so i was looking throught facts and it showed the black and white population are decreasing every year now while the hispanics and asians continue to grow. The black and white population was steadily increasing but started decreasing out of nowhere. Here are the facts http://www.mdreportcard.org/StatDisplay.aspx?PV=35::99:AAAA:1:N:6:13:1:2:1:1:1:1:3