HOOVER, Ala. >> High schools nationwide have canceled or postponed traditional graduation ceremonies to avoid worsening the spread of the new coronavirus, but some plunged ahead with full-fledged springtime commencement exercises as usual, with tweaks to account for health concerns.

Thousands of graduates, parents, siblings and grandparents were invited to a nearly 11,000-seat stadium on Wednesday and Thursday nights in the Birmingham suburb of Hoover, where two high schools — among the largest in Alabama — were organizing traditional commencement exercises despite COVID-19.

Two schools in nearby cities held their ceremonies Tuesday, with chairs for more than 540 graduates spread apart across a football field at Thompson High and a keynote address by the state school superintendent. Few wore protective face masks, and seniors hugged and gathered in tight groups for pictures.

Dr. Michael Saag, who treats infectious diseases at the University of Alabama at Birmingham, said the coronavirus poses too great a risk for such ceremonies since virus carriers without symptoms could unknowingly infect others.

Saag himself became infected in March.

“Having had this before, even if you survive it, which most people do, it’s still a pretty harrowing thing to go through,” said Saag, now back at work.

School officials in Hoover announced the ceremonies in the city’s open-air baseball stadium, after Gov. Kay Ivey had ended state restrictions on the size of group gatherings, as long as people from different households stay 6 feet (1.8 meters) apart.

Hundreds of chairs for graduates were spread across the dirt infield with spectators assigned seats on metal bleachers and in blue stadium seats. Red tape blocked seats to be avoided.

Kathy Murphy, the city school superintendent, said the ceremonies will comply with the rules.

“All of our students will be celebrated, even those who choose not to come, and we understand that. But we will call their names,” Murphy said in a video posted online.

Since Gov. Kay Ivey eased restrictions in recent weeks, cases have risen in parts of Alabama including the capital city, health officials say.

Statewide, Alabama has added as many as 350 new cases per day in the past two weeks, and the state’s average number of new cases has continued to climb. It’s unclear how much of the rise is due to increased testing or increased disease. And there are large numbers of COVID-19 patients hospitalized in Montgomery and Mobile, two other major Alabama cities.

Schools in California planned virtual graduations after traditional events were canceled, and students at an Illinois school walked across a stage in an otherwise empty auditorium. Some systems delayed ceremonies until summer or split graduating classes into smaller groups for live ceremonies. Former President Barack Obama recorded a video graduation speech for seniors.

But Spain Park and Hoover are two of Alabama’s largest, top-ranked state schools. Both are in a heavily populated area, drawing criticism from those who called the ceremonies risky.

As a precaution, the graduates are being given face masks and told not to hug friends, exchange high fives or linger afterward. Tickets are limited to four per student, and all present must wear face coverings. Still, the numbers of potential attendees are daunting at a time when sporting events, concerts, and movies are still prohibited because of crowd concerns.

Some 390 seniors graduated Wednesday night from Spain Park. Everyone had a mask on while entering the stadium though a few in the class and the audience removed theirs once seated and the ceremony started. The event began orderly with ushers directing family groups to seats at least one row and more than 6 feet (1.8 meters) apart.

The Spain Park graduates, in their black robes and masks, spread out in chairs across the baseball infield. Besides the nearly 400 students, faculty and administrators on the field, there were easily more than 1,500 people in the stands.

Another 690 will graduate Thursday from Hoover High, so some 3,450 people could be inside Hoover Metropolitan Stadium then.

Critics say that even with the rules, huge ceremonies could hasten more coronavirus transmission in metro Birmingham, home to more than 1 million. The city of Hoover, with 85,000 residents, sits astride two counties that have more than 1,770 virus cases combined.

Bonnie Kaiser, a 2004 Hoover High graduate who teaches in the Department of Anthropology and Global Health Program at the University of California-San Diego, was among 31 health professionals and system alumni who signed an open letter urging officials to reconsider the ceremonies.

“I think the thing is there’s not a way to do it safely even if everyone has perfect behavior … and we know at a graduation that just will not happen,” Kaiser said.

But parents pleased their children could have a traditional graduation flooded the school’s social media feeds with thanks to school officials. Still, some top-ranked students said they were skipping the celebrations.

Omar Mohammad, a 17-year-old Spain Park senior, organized a protest Saturday outside the graduation site with a few dozen supporters. He called the ceremony, which he skipped, “unsafe and irresponsible.”

“All it takes is one asymptomatic person,” Mohammad said. “This isn’t about graduation … If you get a disease you can spread it.”

Murphy, the city superintendent, emphasized the ceremonies are optional.

South of Hoover in Alabaster, Thompson High School held a traditional graduation ceremony in its football stadium Tuesday night, limiting it to 2,500 guests, or roughly half the normal capacity, but with no masks required. Senior Jael Janae Johnson thanked God for the event in the opening prayer.

“This wouldn’t be possible without your will,” she said.

The social distancing ended for the most part as soon as the ceremony was done. Still on the field, many graduates gathered into groups for hugs and selfies.