With school closed and graduation canceled, the principal of a high school in suburban Dallas set out on April 17 with his wife, a bag of Snickers bars and a mission: visiting each of the 612 seniors at their homes.

Virdie Montgomery, the principal of Wylie High School in Wylie, Texas, said he thought it would take only a couple of days to see each student, deliver a note and a candy bar, and ask how they were doing. It ended up taking 79 hours across a dozen days, and about 800 miles traveled.

Wearing a mask covered in skulls and crossbones — a tribute to the school’s pirate mascot — Mr. Montgomery, 66, took a selfie with each student. He told them the school was a much less happy place in their absence, but that one day they would “look back on this and snicker.”

Then he handed them a candy bar.

“I delivered the same lame joke more than 600 times,” Mr. Montgomery said. “I wanted to see them and make sure they were doing all right.”

Across the country, high school teachers and administrators are going out of their way to recognize their seniors as the coronavirus pandemic has closed schools and forced the cancellation of proms and graduation ceremonies.

The staff at Chesterton High School in Chesterton, Ind., delivered “Class of 2020” yard signs. Dozens of teachers at West High School in Salt Lake City placed personalized yard signs outside the homes of graduating seniors. And the principal, teachers and administrators at Wellington High School in Wellington, Fla., donned masks and gloves to surprise the school’s 626 seniors with yard signs.

In Texas, a statewide stay-at-home mandate went into effect on April 2. At first, Mr. Montgomery said, Wylie High School extended its spring break. But when the school was forced to close for the rest of the year, students’ attitudes changed, he said.

Prom, scholar banquets and other senior traditions were all canceled.

“We are a tradition-laden school,” Mr. Montgomery said. “And golly, they were on the floor with their hearts.”

One of the seniors designed a class shirt, the school board delivered signs to every senior’s yard, and the school hosted a drive-by cap-and-gown pickup for a graduation ceremony that has yet to be rescheduled. But Mr. Montgomery said he didn’t think it was enough.

“The absolute most important thing is that they know that they’re cared about,” he said. “And it has to be authentic. The most valuable gift that you can give to someone is time. I was basically telling them that I care about them.”

One day, Mr. Montgomery and his wife, Pam, traveled 127 miles and visited 14 students. Their record was 91 visits in one day, he said.

“It didn’t really surprise me that much because that’s kind of his character,” said a senior, Brooke Ermias, 18. “But especially in this time, just seeing him at my house was a nice feeling, just knowing that someone would go to all that trouble just for you. And not just me, but my whole grade.”

Madelene Do, 17, the senior class president, said Mr. Montgomery’s visit lifted her spirits and gave her hope.

“It made me feel like I wasn’t alone in this crisis,” she said. “The senior class is suffering. Every senior across the nation is suffering, but our support system is unique.”

Mr. Montgomery tried to keep six feet from the students, though he said it was hard not to hug some of them.

“I’m finishing 43 years in the business, and I’ve never had anything happen like this,” Mr. Montgomery said.

Michael Godbey, the principal of Lincoln County High School in Stanford, Ky., said teachers delivered yard signs on April 21 to each of the school’s 275 graduating seniors.

Mr. Godbey said he spent more than 12 hours that day delivering about 45 signs. Some of the students and their families came out to wave but kept an appropriate distance.

“We miss our kids,” Mr. Godbey said. “We’ve been out for seven weeks now, and it’s normally a busy time with graduation plans and making memories.”

Mr. Godbey said that the school still planned to hold a virtual graduation ceremony over five days later this month. Each senior will come to the school, one at a time, to walk across the stage. Each walk will be recorded and then compiled professionally into a video that might be screened at a drive-in theater, he said.

“We’ve been struggling with how to make this year special for our seniors and how to commemorate them,” Mr. Godbey said. “For some of our kids, this graduation will be the one big time that they get to be celebrated.”

In Vanceboro, N.C., Tabari Wallace, the principal of West Craven High School, and about 70 teachers and administrators delivered personalized yard signs to the school’s 220 seniors on April 27.

They were joined by the members of three law enforcement departments, a fire department and members of the school board. They split into 13 caravans, each with a fire truck in front.

“It was extremely emotional,” Mr. Wallace said. “When they saw their face on their sign, some broke down, some ran over. The kids were running off the porch trying to get to us, just crying. The sheriff had to tell a few of them to back up.”

As he delivered the signs, Mr. Wallace said he also had news: The school was not canceling graduation or prom, but instead was delaying both until a day in either August or December, with graduation to be held in the morning and prom in the evening.

That news brought many to tears, he said.

“I told them to take the sign as a token and as a bridge until I can get them across that stage,” Mr. Wallace said. “I wanted them to know that we are with them, we support them and we love them.”