U.S. schools were counting on widespread vaccinations to help get all students back to in-person classes for the first time since early 2020. Mere weeks into the effort, signs of another taxing year are emerging amid scattershot safety rules and rising Covid-19 among children.

Over the past month, with kindergarten through 12th grade in session, the country has reported almost 1 million cases among those under 18. Though kids typically are less likely than adults to become severely ill with Covid, they increasingly are contracting the highly contagious delta variant. As of Sunday, 2,000 schools nationwide had closed — 18% more than a week earlier, according to the Burbio tracker.