FRANKLIN, Tenn. — Five years ago, Kim Hart’s son underwent an open-heart surgery that got him healthy enough for the family to move from Cincinnati to this quiet suburb of Nashville. Her son has Down syndrome and autism, and she liked that Williamson County had a reputation for caring neighbors and safe schools.

But every day for the past month, she has wondered whether she made a mistake.

It was here that an explosive debate over masking in schools — one of the most effective strategies for keeping students learning in person safely during the pandemic — made the county a poster child for divisions over coronavirus safety measures. A video clip of a county school board meeting last month, showing protesters heckling and threatening medical professionals and parents who supported a universal mask mandate as they left the meeting, drew national attention and a rebuke from President Biden.

As cases in Tennessee surged — the state was leading the nation in new infections per capita earlier this month — many residents of the predominantly white, wealthy county were left despondent that a piece of fabric had become a political statement.

“It’s very dystopian,” Ms. Hart said. “I’m used to arguing with a district to get my kid what he needs. I’m not used to my neighbors screaming at a school board meeting over a mandate that protects everybody.”