In chapter 21 " Imaginary Music" I feel the underlining theme was to always find the joy in life no matter what the situation is. I also feel the way Kozol hits on this, is to never grow up all the way and when the time is right let the inner kid out.
As the chapter goes on, the children face a hard situation because they cannot afford the music equipment and things to have a music lesson in Mrs. Gambles class. therefore Mrs. Gamble made up for it by using imaginary instruments and teaching them the correct technique for certain instruments. though silly, Mrs. Gamble knew how to make it fun and productive.
In high school I feel that a lot of kids my age and younger than me were always held back because school was too boring and there was not enough interest to keep them busy. there was always something else on there minds and the never wanted to focus on the task at hand. in my opinion that was not entirely their fault. The teachers and instructors could have done a lot to make things more interesting and keep the interests of the students.