The teacher in Boyle Heights is unfriendly to Jeanne because people in California are becoming more and more suspicious of Japanese-Americans.
Jeanne comments that the experience with her teacher in Boyle heights was the first time she felt “outright hostility from a Caucasian” (Ch. 2, p. 16). Her teacher does not seem to appreciate that she is struggling. The teacher ignores her and does not make any attempt to explain anything or help her out.
As an adult, Jeanne understands why the teacher was so cruel to her, given the social landscape of the time.
Public attitudes toward the Japanese in California were shifting rapidly. In the first few months of the Pacific War, America was on the run. Tolerance had turned to distrust and irrational fear. (Ch. 2, p. 16)
The author blames the “hundred-year-old tradition of anti-Orientalism” rearing its ugly head. California had a long history of discrimination against Asian immigrants, and this gave them a good reason to treat people of Japanese origin badly.
There is no excuse for this kind of behavior, of course. Having an explanation does not make Jeanne feel any better now, nor would it have made her younger self feel any better then. The hypocrisy of the American people in triumphing democracy in Europe while rounding up Japanese-Americans in internment camps is a shame that can never be washed away.