The Peninsula School District spent at least $300,000 to clean the building and its ventilation system. Workers bore through walls to find and eradicate mold and replace dingy carpets with floor tiles.

A final cost figure won't be available until more workers' hourly and overtime bills are paid, deputy superintendent Marcia Harris said.

During the closure, Artondale's 470 students studied in portable buildings and makeshift classrooms at four other district schools.

Staff said they were concerned about whether the school is entirely clear of the excessive dust and mold that gave some people headaches, itchy eyes, sinus troubles, breathing problems, rashes and other mysterious symptoms.

But Harris said two independent firms tested the school's air last week and found the building fit to occupy. The district will try to accommodate any student or staff member who still has problems at Artondale.

State and county health department officials don't certify such schools for re-entry, Harris said, but they have monitored the cleanup.