In the Freedom Writer's Diary, a true story of Gruwell's teaching experiences, the students, African-American, Asian-American, and Latino, have many reasons to avoid others not of their own races and/or ethicities. Gruwell had a great deal to overcome. Those fortunate enough to have not grown up as these children did will probably have a difficult time understanding this.
First, these students were raised in ghettos, small neighborhoods made up only of their own races and ethnicities. They had little or no exposure to those outside their ghettos. And they lacked the wherewithal to enter the larger world, financially and psychologically.
Second, the parents of these students no doubt discouraged them from getting to know others unlike them. There was good reason for this. These parents had experienced nothing but racism and hatred from others. The norm, sadly, in their lives was to endure the prejudice of others, based on race, ethnicity, and a strong American dislike for immigrants in general. These parents probably thought that they were protecting their children from all of this.
Third, these students were living in a gang culture. Gang affiliations were based on race, ethnicity, and neighborhood. To show allegiance to their respective gangs, they could not mingle with those from other gangs. You may have seen the film West Side Story, which, for Hollywood, is a fairly accurate representation of this world, although none of Gruwell's students were breaking into song at dramatic moments.
Finally, all of these students had good reason to avoid white people in the education system. It took a long time for Gruwell to gain these students' trust. Teachers and administrators had consistently let them down, with neglect, low expectations, prejudice, and even cruelty. It is not at all surprising that they had no reason to think well of white people.
It is a remarkable testament to Gruwell's powers as a teacher that students, having led such lives, could place their trust in her, enough to even make them care about the problems of others, not just their own problems. It is their engagement over the Holocaust that turns them into empathetic people, and it is this that allows them to get past all of the limitations that they have had all their lives, limitations created by their environment.