First-grade teacher Mona Sobel reads to her class during the first day of school at Bladensburg Elementary on Aug. 19. (Amanda Voisard/For The Washington Post)

A group of retired and current teachers from Bladensburg Elementary School in Prince George’s County gets together at least twice a year to talk about families, share fond memories and discuss the latest in education.

But the last time the group met, they realized something they hadn’t noticed before: Mona Sobel was the only one among the long-serving educators who was still teaching at the school.

When Sobel greeted her 26 students in Room 5 for the start of the school year three weeks ago, she marked the beginning of her 40th year as a first-grade Bladensburg teacher.

“I still love what I do,” said Sobel, 61, who decided that she wanted to become a teacher while working as a teenage babysitter more than four decades ago. “I always wanted to work with children, but the little ones.”

Sobel sat in her white rocking chair during a recent class, instructing her students to remove their science books from their desks, bring the books over to the rug near her and sit down in a circle.

“I shouldn’t hear a sound,” said Sobel, wearing tan capri pants and a turquoise-colored blouse and shrug. The students quietly moved from their seats and sat on the floor with their legs crossed.

Today’s lesson: nonliving things.

“Nonliving things were never alive,” Sobel told the students. “They do not need food or water. They do not change.”

Sobel began calling on students, asking them to name something in the classroom that is a nonliving thing.

One said “chairs.” Another answered “books.” When Stephanie said “globe,” the students and Sobel placed their finger on their nose. That is what the class does when someone uses one of the “Wordly Wise” vocabulary words. Some of the other words of the week: “vacation” and “capitol.”

Teachers, principals and even curricula have come and gone, but Sobel has remained a constant at the school, which about 700 students attend. It is not unusual for her to teach the children of some of her former students.

Sobel said she has learned to “go with the flow” as curriculum and teaching methods change, which they seem to do every few years. She said the new Common Core standards, which 45 states have adopted as part of a nationwide effort to standardize U.S. education, “seem to be a lot of the things we did back in the ’70s.”

The biggest change she has noticed over the years: the lack of resources.

“Schools don’t have the money for supplies, sometimes even to make copies,” she said. “A new teacher, I don’t know how they can afford what they have to buy. Thank goodness for the dollar store.”

Shirley Eden, who retired after working 30 years as a kindergarten teacher at Bladensburg, said she can tell how much Sobel still enjoys her work.

“She’s always anxious about going back,” Eden said. “She just never tires of it. . . . The kids just love her. I can’t remember a kid that didn’t learn under her.”

Laurel Gombatz, who retired in 2000 after working nine years as a reading specialist at Bladensburg, credits Sobel’s success to her teaching style.

“She’s very structured and organized,” Gombatz said. “Mona starts planning for the next year at the end of the previous school year. She makes individual changes depending on the children she has, but by and large, she is ready to roll.”

Sobel calls herself old-

“I’m strict, but I believe in rewarding good behavior,” she said.

Olga Noriega’s son, Marcos, was a student in Sobel’s class seven years ago. Noriega said she appreciated Sobel’s sternness. “Marcos had a lot of homework and he was not pleased at the beginning,” Noriega said. Before long, she said, Marcos had picked up Sobel’s knack for organization and would often correct her by countering, “That’s not what Ms. Sobel said.”

“He really listened to her, and he liked her,” Noriega said.

On a recent day, Sobel called each student over to her desk to review their papers after a reading lesson.

“What bad thing happened to Benny?” she asked.

“He was going in the water,” Monica said.

“And how was the water?” Sobel asked.

“It was cold,” Monica answered.

“Very good, Monica,” Sobel said. Monica beamed with pride as a smile flashed across her face. Sobel placed her hand on the girl’s face and squeezed her cheeks before she went back to her desk.