“I really feel scared to say that we’ve turned a corner,” she said. “The things that we were struggling with, even outside of Covid, are just still there.”

In Ms. Barros’s classroom at the Tulsa School of Arts and Sciences, many students require intensive support. One boy didn’t attend a single virtual class as a sixth grader or return when the school building reopened last spring. It’s Ms. Barros’s job to keep him tethered to school.

When another student started clutching a stuffed toy shaped like an avocado, Ms. Barros didn’t press her for a reason. And when one of Ms. Barros’s top students started having panic attacks in class, she helped come up with a plan to calm her heavy breathing. Her school has noticed an uptick in thoughts of self-harm, negative self-talk and meltdowns. More students are asking to see the counselor.

Two years into the upheaval, teachers are depleted. On top of the needs in their classrooms, teachers and their unions have faced scrutiny over school shutdowns, vaccine and mask mandates and Covid safety protocols, leading to labor strife in Chicago and elsewhere.

Some teachers have begun having doubts about their ability to keep going. As three colleagues departed midyear for higher-paying jobs outside the classroom, Ms. Barros, who has taught for four years in Tulsa, found herself scrolling job listings earlier this winter. Like most, she’s sticking it out. “For a while, I was in that victim mentality of ‘woe is me,’ but I do have choices,” she said. “And I’m choosing to stay because I love this.”

But America’s schools remain fragile. As teachers catch their breath after the latest wave of Covid cases, many are teetering between cautious optimism and lingering exhaustion.