In the Chapel Hill-Carrboro City Schools in North Carolina, a “significant” number of teachers have said they will skip work on Wednesday, the district said. The roughly 12,300 students are to stay home, and the day will be an optional teacher workday.

“It is my determination that we will not have enough staff to safely run our school district,” the interim superintendent, Jim Causby, said in a letter on the district’s website.

Both school districts cited the observance of International Women’s Day as the reason for the staffing shortages. Nationwide, more than three-quarters of all teachers are women, according to the National Center for Educational Statistics.

The leaders of the Women’s March on Washington, which drew more than a million demonstrators the day after the inauguration of President Trump, have encouraged women to strike on Wednesday to highlight their economic importance and power. The movement, which grew out of concerns about Mr. Trump and has spawned protests around the world, has emerged as a vocal champion of women’s rights.