Raleigh, N.C. — The state NAACP is calling on the U.S. Department of Education's Office of Civil Rights to "reinvigorate" its investigation into the Wake County Board of Education, saying the school system's new student assignment plan "has been an abject failure" when it comes to keeping schools economically diverse.

The group on Friday submitted a supplement to a civil rights complaint that it filed in September 2010, saying the district's assignment policy violates the Civil Rights Act of 1964.

The student assignment plan, often referred to as a "controlled-choice" plan, allows parents to rank among a list of schools where they would prefer their children to attend. The school system, however, ultimately decides placement based on the feedback.

The NAACP cites a report by Raleigh Public Record that shows Wake County schools with the most students of color will see a 4.65 percent increase in the number of students receiving free and reduced-priced lunches when new plan kicks in with the 2012-13 school year.

In contrast, the NAACP says, schools in predominantly white areas of the county will incorporate fewer poor students.

"In short, our worst projections will be realized this fall. Our children – black, brown and poor – will be funneled into schools that are already black, brown and poor," state NAACP President Rev. William Barber said in a letter to the education department.

The NAACP has been one of the most vocal critics of the board policy change in 2009 to stop busing students for socio-economic diversity.

For a decade, the school system shifted students to schools across the county so that no school had more than 40 percent of its population receiving free or reduced-price lunch.

The school board voted to change the practice, saying it wasn't working.

But opponents of the new plan said it would lead to segregation, high teacher turnover and a lower quality of education for low-income students.

The Office for Civil Rights has been looking into the NAACP complaint but has yet to make public any findings.