Of the cadre of non-educators--business leaders, military men, government officials, lawyers--who have been called on to transform large urban school districts in recent years, Paul Vallas has been at it the longest and, in the minds of many, is the one with the best track record. Since 1995, he has tackled the third- and eighth-largest districts in America--Chicago and Philadelphia. Both of them are old-politics big cities with school systems long steeped in racial tensions and marked by tough unions, deteriorating buildings, and white and middle-class flight. Intensifying poverty and racial isolation accompany escalating demands for better student outcomes. After jump-starting schools in Chicago and Philadelphia, Vallas is giving new hope to the hurricane-battered city on the Mississippi. Now, Vallas is focused on what may be his biggest challenge yet as superintendent of the Recovery School District (RSD) in the ruined city of New Orleans. (Contains 1 figure.)