I would say that it is actually the ambitious students that get less of their historical knowledge from school textbooks as they gain most of their knowledge from cram schools which use their own teaching material.
I have taught at two Japanese universities that are considered quite prestigious( one private, one
national) had quite a lot of discussions with students about history textbooks and their knowledge of Japan's modern history and my conclusions are similar to Earl's.
When conducting my research on history textbooks I had a number of discussions with high school history teachers and people from publishing companies and quite a few of them said that the importance of history textbooks in shaping students' understanding of history is overestimated.
At the end of the day it is very much up to the teacher how a certain event in Japan's history is taught in class and this is particularly relevant for post Meiji history because the narrative in the textbooks is very limited. I think that in most textbooks the whole Asia- Pacific War is covered in less than 15 pages . At the same time some students told me that they never got past Meiji in their history classes because the teachers saw their main task to prepare the students for high school/ university entrance exams and the latter rarely contain questions from Showa.

Yours,
Alexander Bukh
Victoria University of Wellington