Students at Langenburg High School returned to class Monday after the building was closed due to air quality concerns.
Officials say samples taken from the school indicate it is safe for staff and students to return.
Classes resumed for students in grades 10 to 12, while those in grades 5 to 9 are scheduled to return Wednesday.
The school was closed earlier this month after some students and staff began experiencing respiratory problems.
A public meeting is scheduled for Tuesday to provide parents with an update on the situation.
