1. In New Orleans, we don't have "higher ground".
2. School bus drivers are not first responders. They are not trained or paid for stressful, hazardous duty requiring capacity for independent thought and quick decisions. They certainly have not signed up for it. A day before Katrina's landfall, school bus drivers were taking care of their families and property and considering their options like everyone else. The notion that such people are available on short notice to man a mass evacuation (to where?) are, to put it mildly, unrealistic.
But in New Orleans...
You cannot excuse the incompetence that easily.