Quyen Nguyen received a mysterious postcard in the mail this summer from Arlington public schools. “The Traveling Trolley will be in the Carlin Springs neighborhood,” it announced, listing dates and times.

Unsure what to expect, he took his 5-year-old son out to the corner Wednesday a little before 6:15 p.m., joining other waiting families minutes before a bright blue bus pulled up and offered them a ride to the neighborhood library.

A beaming Kevin Nguyen was the first child to bound up the steps.

“Welcome to the Traveling Trolley, boys and girls,” said Erin Watson, a family engagement specialist for Arlington public schools.

The breezy bus ride is the school system’s latest effort to encourage summer reading — and to get kids like Kevin, who will start kindergarten at Carlin Springs Elementary this fall, excited and ready for school.

On four Wednesday evenings in July, two bright blue buses — rented at a discount from an Arlington family — pick up students from three elementary schools and take them to their public libraries. Educators, who advertised through backpack fliers, robo-calls and postcards, are hoping to reach younger children, from pre-kindergarten through second grade, and those who speak another language at home.

Arlington is aiming to counteract the stubborn summer slide in reading skills that often affects students from poor families who have fewer books at home. There is a “summer mailbox” program at high-poverty schools to send books to students, and Abingdon Elementary School has a mobile library that travels to neighborhoods throughout the summer.

At Carlin Springs, where many students are learning English as their second language and 85 percent qualify for free or reduced-price meals, librarians visited the school before the end of the year to show students the kind of books they could borrow. Some teachers took their entire class to sign up for library cards.

Principal Corina Coronel promised to host a dance party in the gym this fall for students who took the trolley to the library.

After the first stop Wednesday night, the trolley lumbered past apartment buildings and a group of kids kicking a soccer ball down the sidewalk. More than 20 children were waiting with their parents at the second stop, some with their arms full of books to return.

They took turns high-fiving Ms. Gorsky, a teaching assistant, as they boarded.

Brian Orellana, 6, wedged into a seat between his mother and his older brother and bobbed his head to guitar music that a high school student from Washington-Lee was playing.

“Whee!” Brian said as the bus got going again.

Watson, dressed in a jacket depicting a map of the world, started a game of geography trivia. Each week, students learn about a different continent.

“I will give you a clue,” she said, “On this continent, you will find many penguins.”

When they arrived at Glencarlyn library, the students gathered around to hear the librarian read two stories about penguins. The children then made their own penguins with glue sticks and construction paper.

School system officials said the events are intended to be educational for parents, too. As the students worked, parents were invited to another part of the library for a financial literacy presentation from a credit union employee.

Parents can learn about the library system and other community resources. They can also pick up parenting skills, such as how to read aloud to children in a way that keeps them engaged.

During the free time that followed, teachers helped students select books at their reading level.

After about an hour, another group of students arrived at the library, and it was time to board the bus home. Children got popsicles and pencils for the road.

Kimberly Solano, 6, said it was her second time taking the trolley. She loves it. “It’s like a bus, but there’s no windows!” she said.

She ran up to her reading teacher, Kathie Coyne, for a goodbye hug. “I love you!” she said.

Coyne said she had worked one-on-one with Kimberly last year because she was behind in reading. But by the spring, she had caught up and excelled. At the library Wednesday night, she did not need coaching to find books.

“She just loves to read,” Coyne said.