Queen Atlas Tuttles the First, a Maryland diamondback terrapin raised by students at Sandy Spring Friends School, heads out into the wild of her natural habitat at Poplar Island, in the Chesapeake Bay, on April 23. As part of a program through the National Aquarium in Baltimore, the students received the hatchling in the fall and tracked her growth for scientists’ records. (Kiki Vargas)

It was bittersweet when fifth-graders at Sandy Spring Friends School said goodbye to one of their favorite classmates last week. He was an interesting friend from the beginning and needed everyone’s help. They even dubbed him king of the fifth grade.

King Atlas Tuttles the First, a diamondback terrapin, spent the school year with the students and returned last week to its natural habitat on Poplar Island, in Talbot County, along the Chesapeake Bay, after months of being cared for and studied by the students.

When the terrapin visited the National Aquarium in Baltimore recently for a pre-release checkup and implantation of a microchip for tracking, the students were surprised to learn that their king was really a queen.

The students, under teacher Kiki Vargas, were part of the National Aquarium’s Terrapins in the Classroom Program. The program allows students to learn more about the Maryland state reptile while scientists collect data comparing the hatchlings raised in the classroom and those raised in the wild.

“From an educational perspective, it’s invaluable, teaching kids about environmental awareness, how to treat their habitat,” said Willem Roosenburg, a professor in the Department of Environmental Sciences at Ohio University in Athens. Roosenburg runs the program. “The jury is still out on the conservation value. We are still collecting data.”

Roosenburg said the program begins in the fall, when the terrapin hatchlings from Poplar Island are about the size of a quarter. The hatchlings are distributed to volunteers, mostly classrooms, then returned in the spring, big and healthy.

“Of course, they feed them like crazy and spoil them,” he said.

Vargas said King (or rather, Queen) Tuttles was the size of a cookie when they got her. She grew to the size of a large hamburger. That is much bigger than the hatchlings that spent the winter in the wild, which Vargas saw when she released Tuttles.

“In the wild in the winter, [Tuttles] probably would be hiding in her shell,” said Jack Thompson, 11, of Bethesda. “She wouldn’t have been fed as much, so she would be smaller.”

Bridget Byrne, 11, of Silver Spring said the class fed their terrapin aquatic turtle food and sometimes live crickets, plus liver once a week.

“She didn’t like the liver,” Bridget said.

The students also were responsible for keeping Tuttles’s aquarium clean, monitoring water temperature and maintaining a log of her weight, size and food consumption.

“The best thing the kids learned, I think, is the difference between raising a pet and caring for wildlife,” Vargas said. “Many of them have household pets, but she was a wonderful conduit for loving the Bay and learning about what her future life will be like and learning about Poplar Island.”

Vargas said that when Tuttles came back from her checkup in Baltimore, the students knew they only had a few weeks left with her. They talked about the fact that she was not their pet and they always knew she would go back to her real home.

The students, she said, wrote their hopes and dreams for their terrapin on sticky notes and invited the school’s other elementary classes to say goodbye through notes, too.

“They were beautiful,” she said. “They said things like, ‘We hope she will find a family and best friends’ and ‘we hope she will live to an old age.’ ”

For now, though, they have to get used to a classroom without their special friend.

“Now, she’s gone, and she left a heavy footprint on our hearts,” Vargas said.