The schools, a national embarrassment, were closed for six months and restarted from scratch. The system was turned over to charter operators, who got the leeway to hire new teachers and have been held accountable by strong schools commissioners. Before the storm, three in five students attended a failing school; now fewer than a fifth do.

This education experiment gave people the confidence to push an overhaul of policing, city procurement and other public services. The business community, which had holed up in the city’s higher-ground residential areas or across Lake Pontchartrain, re-engaged in civic life.

Political change has followed. Mayor Ray Nagin—who blamed the feds for the city’s catastrophic response to Katrina—was replaced three years ago by another Democrat, Mitch Landrieu. Mr. Nagin was indicted last month on 21 corruption counts. Mr. Landrieu enjoys approval ratings in the seventies. The budget was balanced. He upgraded the airport and opened a new street car line along Loyola Avenue in time for the Super Bowl.