The coming of age theme involves a main character or set of characters going through a large change, pushing those individuals into the harsh realities of life. Essentially this theme can work hand in hand with others such as loss of life and grief. Many novels written for a sixth grade audience include this theme due to the severe changes they go through including puberty and changing schools.
A powerful novel that uses this theme is Katherine Paterson 's "Bridge to Terabithia." The story involves a set of main characters who, through friendship and imagination, discover the world of Terabithia. The coming of age theme kicks in when Leslie, one of the main characters, dies trying to find her way to Terabithia on her own. Jess, the other character, is then left struggling to find his way back to their magical world without her.
Alienation is another large theme bridging the gap between elementary school and junior high. This theme comes into play when a character alienates herself while trying to find a way to bridge the gap between her little island and the rest of the world. This theme works well for those moving from one school to another due to the sheer size differences and sometimes the loss of old friends.
One novel geared toward sixth graders for this very reason is "The Island" by Gary Paulsen. The story itself revolves around the main character Wil Neuton. Like most boys his age, he follows a daily routine, along with leaving home and rowing far off shore to his little island. The island serves as his escape from the other tensions rising in his life, but he'll have to return to shore to face the school bully if he's to bridge the gap between himself and the world swirling around him.
Death is one theme that spans across all age groups, including novels meant for sixth grade. While many students may not need to face grief and loss in such extremes, leaving their elementary school and moving into junior high is fairly similar. Children will lose old friends, either due to attending different schools or falling into new groups, but they'll also make new ones.
Katherine Paterson 's "Bridge to Terabithia" handles this theme amazingly well. Not only does the remaining character learn to grieve the loss of his best friend, he also finds new friendship with his younger sister and their school bully.
Friendship is one theme children start reading about around the same time they start going to school. For children migrating from a small elementary school to a larger building for junior high, holding onto the friendships they have from "home" acts like a security blanket. Some of these friendships will pull apart and then come together again, bringing newer friends to the group in the process.
"The Chronicles of Narnia" series by C. S. Lewis addresses many themes, including faith and friendship. The friendship that Peter, Susan, Edward and Lucy share as siblings grows even stronger once they find themselves within the world of Narnia. While Edward does go with his own group for a while, he soon finds his way back to familiar faces, the ones who came along with him from "home." Meanwhile, the other children make friends with the magical creatures of Narnia, assisting in their search for Aslan, the great lion.