Letters From Abroad by Bailey West

For the child of an active military service member, making friends was not always easy, but when Benson Gladwyn arrived at Mrs. Compton’s fifth-grade class, he and Selena Francis became best friends.
When Benson’s family had to move away, he and Selena planned to stay in touch, but life happened, causing them to lose contact.
Almost twenty years later, Benson, serving in the military overseas, receives a letter from his long-lost friend.
A friendship is reunited. A bond renewed.