PORTLAND, Ore. (AP) — The Portland, Oregon, school board ended an in-person meeting amid controversy over a proposed COVID-19 vaccine mandate for children 12 and older after unmasked protesters showed up and refused to don a face covering.

The board that oversees Oregon’s largest school district resumed its meeting with online streaming Tuesday after protesters refused to comply with requests from security guards to put on masks, according to a statement from Portland Public Schools.

Some of the protesters were not from Portland but traveled from elsewhere in Oregon and Washington state, The Oregonian/OregonLive reported Wednesday. Earlier in the day, about 500 students walked out of class in favor of the proposed vaccine mandate.

Rules to mitigate the spread of COVID-19 in schools, such as a statewide school mask mandate for all children, have generated protests in other school districts and school boards and superintendents are often the focus of such actions.

In Redmond, critics of state mandates have crowded board meetings and dominated public comment periods. In Adrian, school board members voted to fire Superintendent Kevin Purnell when he refused to buck state policy, the newspaper reported.

More on the COVID-19 pandemic

The Portland school board is set to vote on the vaccine mandate for students older than 12 on Nov. 2.