Six classrooms at Black Mountain Middle School showed high mold-spore levels in preliminary testing, Poway Unified School District confirmed, making it the second campus in the district disrupted by mold concerns this month. Rooms 1005, 1012, 1013, 1014, 1015 and 1016 returned the elevated readings, while eight other classrooms — 402, 807, 1001, 1002, 1003, 1004, 1006 and 1017 — showed only low levels of mold spores, according to the district.
As reported by NBC 7 San Diego, the district said classes were reassigned before the start of the school year after concerns arose about buildings 10A and 10B, and visible mold was reported in room 1016. Poway Unified sent a letter to families and staff confirming the mold and moisture issues, and rooms 1016, 10A and 10B were recleaned before the 2026-2027 school year began on August 10. Even after that recleaning, the station reports, a mold odor persisted in some of the spaces.
Independent Testing Underway as Final Results Loom
The district contracted an independent industrial hygienist to collect classroom air samples, and district officials have been working with that hygienist to establish room-by-room recommendations for reoccupancy, the outlet notes. The hygienist advised that the preliminary data should not be treated as a final assessment. Poway Unified said it was awaiting final laboratory data from the air sampling, with both that data and a final assessment expected today, and the district said it would provide a further update to families on the same day.
The situation echoes what unfolded just days earlier at Del Sur Elementary School, where elevated spore counts forced the district to relocate its entire student body to nearby Stone Ranch Elementary School for roughly a month while remediation continued, according to CBS 8 San Diego. Del Sur students were forced to relocate after the mold delayed the start of their school year, and the station reports that Poway Unified hired Belfor Property Restoration for physical remediation and Air America Testing for environmental evaluations and air quality certification, with crews installing HEPA air scrubbers and industrial dehumidifiers. Hoodline previously reported on that campus's start-of-school mold delay.
A Pattern of Moisture Problems at Del Sur
Del Sur Elementary, which opened in 2008 to serve the master-planned Del Sur community near Black Mountain Open Space Park, has faced recurring moisture issues before this year. The campus dealt with a window leak in August 2023, and a 2024 testing round — prompted by a parent petition signed by more than 300 community members — confirmed mold spores in six of 17 campus locations, per the same Hoodline reporting. A classroom teacher had even performed independent testing before the district's own 2024 assessment.
Black Mountain Middle School serves 1,060 students in grades 6 through 8 in the Rancho Peñasquitos community and last underwent a full facility remodel in 2009, according to the school's own information. Poway Unified operates 40 schools across roughly 100 square miles of northern San Diego County and employs about 4,000 teachers and support staff, making campus-by-campus moisture management a persistent logistical challenge for the district.
No Federal or State Spore Limits Complicate Response
Part of what makes these episodes difficult to resolve quickly is the absence of any legal standard for what counts as dangerous. Neither the California Department of Public Health nor the U.S. Centers for Disease Control and Prevention maintain statutory exposure thresholds or numerical limits for airborne mold spores in classrooms, according to CBS 13, and public health agencies generally recommend against airborne testing altogether given the lack of established health benchmarks. That leaves districts like Poway Unified to set their own room-by-room reoccupancy thresholds in consultation with hired hygienists rather than a mandated standard.
The U.S. Environmental Protection Agency does distribute voluntary “Indoor Air Quality Tools for Schools” guidance focused on preventive maintenance and moisture control, and the agency's research ranks indoor air pollution among the top environmental public health risks. California law separately requires districts to provide 180 days of instruction annually, but it allows districts facing emergency delays to file Form J-13A waivers that preserve full state funding without extending the calendar — a mechanism that has already come into play once this month at Del Sur.
Leadership Faces Scrutiny Amid Facility Concerns
The mold cases arrive as Poway Unified operates under relatively new leadership. Superintendent Dr. Ben Churchill took over the district in December 2024, following the April 2024 termination of former superintendent Marian Kim Phelps after a district investigation. Churchill previously spent eight years as superintendent of Carlsbad Unified, and now faces parent questions over facility maintenance and communication as a second campus grapples with mold just weeks into the new school year.
