LOS ANGELES (AP) — The Los Angeles Unified School District said it will prohibit students from wearing cloth masks as the highly transmissible omicron variant of COVID-19 continues to spread.

The district says starting Monday, students must wear “well-fitted, non-cloth masks with a nose wire” at all times. Higher grade masks will be made available to students upon request.

The shift away from cloth masks was prompted by guidance from county health authorities. LAUSD will allow exemptions to mask rules for some students with disabilities.

The LA County Department of Public Health said Saturday that the seven-day testing positivity rate remained “very high” at 16%.