The following Executive Order (PDF file) is dated Sep 1:
...WHEREAS, there is an immediate need for mass transportation to move citizens to shelters and other safe locations from disaster areas; and
WHEREAS, given the current exigent circumstances, buses are the most reasonable and practical mode of mass transportation to move our citizens to safety;
NOW THEREFORE I, KATHLEEN BABINEAUX BLANCO, Governor of the state of Louisiana... do hereby order and direct as follows:
SECTION 1: Each Superintendent of Education for each school district in Louisiana that remains substantially operational following the passage of Hurricane Katrina shall contact the Office of Homeland Security and Emergency Preparedness... and provide an inventory of school buses and bus drivers in their district;
SECTION 2: As determined by the Office of Homeland Security and Emergency Preparedness, such buses shall be made available to be used as necessary for the mass transportation of Hurricane Katrina evacuees, accompanying law enforcement personnel, and necessary supplies to and from areas of concern to areas of safety;
SECTION 3: The Office of Homeland Security and Emergency Preparedness is hereby authorized to commandeer and utilize such buses for such purposes;...
UPDATE: The original post said this was ordered on Sep. 1. The actual date this was signed was Sep. 2.