Your article:
"When Rosen happened upon them, the children were sitting in an orderly way at the end of his driveway. They appeared out of breath and he could see the fear and distress on their faces. While he is unsure how the students escaped the school, Rosen believes they must have run some portion of the road before being picked up by a school bus driver, who was with them when Rosen found them."
As to why the bus driver may not have taken them over to the firehouse: [s]he obviously hadn't gotten the memo at that time. It hadn't been issued yet.
Hope that helps.