Teachers and students were evacuated Monday morning from Prairie Park School for less than a half-hour, spurred by a fire alarm that provided a teachable moment although the alarm itself would turn out to be false.

“The staff did an excellent job getting the students out of the school,” said Doug Green, a division chief for Lawrence-Douglas County Fire Medical, serving as shift commander at the school. “They did a great job.”

No specific cause for the false alarm was immediately evident, but Tom Bracciano, the Lawrence school district’s director for operations and facility planning, figures a dirty sensor might have been to blame. Carpenters had been working to repair a leaky roof above the lobby, but were not using materials or equipment that could have sparked a fire.

By 11 a.m. students had filed back into the gym, and then to their classrooms, to finish off yet another day — another step closer to summer vacation, which begins March 26.