Hockinson High School’s 668 students were sent home Tuesday morning due to a malfunction in the school’s electronic heating system. The evacuation was a precautionary move, Hockinson Superintendent Michael Grubbs said. No students reported illness due to the gas smell that permeated through portions of the school. Classes are expected to resume today. The natural-gas odor resulted when one unit of the school’s heating system failed to electronically ignite, Grubbs said. The malfunction caused the gas to return to the system, creating an odor that was reportedly strongest in the school’s gym.“As the smell increased, we evacuated the kids around 10 this morning,” Grubbs said, noting the decision was made to “make sure the kids were safe.”Such an evacuation is rare at Hockinson High, 16819 N.E. 159th St.“This is the only time it’s happened here in the eight years I’ve been here,” Hockinson High Principal Brian Lehner said.Students attended classes for around two hours before the evacuation. For that reason, Grubbs said he did not believe they would have to make up the school day.Administrators were able to ventilate the front office and commons area before the school day began, but were unable to do the same with the school’s classrooms. The classroom windows are kept closed due to safety concerns.