I agree with you Michaela.
I don't know the geography down there at all. It seems that there are higher spots in the area. IF the buses could not get all the way to Texas (and it seems like they could) couldn't they also have just transported them to higher ground to some sort of temporary camp while other more suitable transport became available? Either way, the buses would have been very useful.
It is fine to say that the levees should have been stronger. Of course they should have been and it seems the authorities dropped the ball on that too. The fact is, the levees broke/failed and huge numbers of people needed help to leave town. School buses would have been a very useful in this task.
I am constantly amazed that a city situated below sea level would not have an emergency evacuation plan for a possible flood. That is pretty unacceptable.