Study is HERE. From the study:
After seven years (the end of elementary school), children in public housing in Montgomery County’s most affluent half of elementary schools performed eight points higher in math .. and five points higher in reading ... than otherwise similar children in public housing who attended schools with greater than 20 percent poverty. Within education research, these are large effects since relatively few educational reforms demonstrate positive effects of this magnitude.
Perhaps most important, the children in public housing who attended low-poverty schools began to catch up to their non-poor district-mates over the course of elementary school; by the end, they had cut their initial achievement gap in half.