The most significant theme in The Freedom Writers Diary is tolerance and understanding. Gruwell’s students hated one another for no reason other than that they thought they were supposed to because of gang histories and stereotypes. Gruwell taught them that they actually had more in common than they wanted to believe. Many of the students had lost a friend or loved one to senseless violence. Many of them had been abused or molested. Many of them were victims of substance abuse. Because the education system had deemed them “at risk,” Gruwell's colleagues were unwilling to devote the time, energy, and attention to the students that would foster a positive, safe environment for them to not only tolerate their differences but accept and even appreciate them. Enter Erin Gruwell, an idealistic young teacher who was not willing to take no for an answer from students, parents, or administrators.

What The Freedom Writers Diary teaches readers is how empowerment can change lives. Once Gruwell convinced her students of their self-worth, they began to see their potential. The students felt empowered to take academic and intellectual risks in the classroom; the first 150 Freedom Writers all graduated from high school, and many went on to attend college when most believed that they would not even make it through the ninth grade. Perhaps more important, they felt empowered to befriend those whom they had previously dismissed as “the enemy.” Additionally, they were empowered to believe that they could be successful; for many of Gruwell’s students, she was the first person in their lives who had believed that they had potential.

Along with empowerment, The Freedom Writers Diary demonstrates the importance of self-worth. Because so few of Gruwell’s students had ever had someone believe in them, half of her battle was showing the students that they were not only capable but worthy of receiving a good education. She showed them that they did not have to simply become a product of their environment, which expected them to turn to a life of gangs, drugs, and violence. Rather, she taught them that once they believed in themselves, they would succeed.

The Freedom Writers Diary also explores the power of writing. Most of Gruwell's students had never thought to express their feelings in writing; in fact, most of them hated to write at all. However, Gruwell taught them that writing could be a powerful practice and that they could find in it the strength and inspiration they so desperately needed. Gruwell used first-person accounts by teens who struggled through their own set of difficult circumstances. Suddenly, students who had never even heard of the Holocaust not only read Anne Frank: The Diary of a Young Girl but also won the Spirit of Anne Frank Award for their courageous work. Students who had no idea where Bosnia was located not only read Zlata's Diary but also met Zlata Filipovic, who grew up in a war-torn country and had to flee for her own safety. By employing their minds and their writing skills, Gruwell’s students learned that answering violence with violence was not a solution. They learned, instead, that they needed to be a “catalyst for change.”