The update was announced to parents on Wednesday, and campus administrators observed increased humidity and visible mold in certain areas inside the building during the summer.
The district said it immediately conducted testing in July, which showed increased mold levels in the air and on surface samples. Further testing was done, and officials said there were two contributing factors.
Westwood said the HVAC system could not effectively manage the building's humidity, and moisture from the HVAC system saturated parts of the roof deck and other areas of the building.
School officials said there had been a planned repair of the HVAC system in the coming weeks, as well as a roof repair. The school also promised additional surface cleaning, and said the safety of students and staff comes first.
"We recognize that this news is difficult and may create challenges for your family. We sincerely apologize for the disruption this causes and understand the inconvenience and uncertainty it brings. While we know everyone is eager to begin the new school year, we believe taking the time necessary to complete this work is the only responsible decision. The safety of our students and staff must come before any timeline."
Officials did not give an exact date for when students would return to campus, but said the next update is planned for Friday, August 7.
Friendswood ISD did say no other campuses were affected and they will start as scheduled.