Caution: You need to be able to read Japanese if you really want to act like this.
On English opinions web, there are many big demagogies of what Japanese schools teach, including that we are not taught our war crimes. And very many people insult Japanese education by false accusations without reading real Japanese textbooks and other educational contents. It appears that also Japanologists are so, too. So I create this manual.
In Japan, screened textbooks of primary education and secondary education are highly standardized by Japanese government's course guideline and the government's screening. Primary schools and middle schools mainly use the screened textbooks. (See: Textbooks of Ministry of Education, Science, Culture, and Technology and 意外と知らない“日本の教科書制度”(1) - 学びの場.com("Japanese Textbook System" that Surprising Many don't Know. - Place for Learning) by Uchida Youkou's Education General Institutie) In addition, we use reference books and kids study books along the guideline. About the case of primary schools and of middle schools, the screened textbooks are bought to each pupils by the government every year, after the adoptions of municipalities, of national schools, and of private schools.(Source) And about the case of senior schools, each pupils have to buy the textbooks selected by the schools. So the textbooks used in any schools are up-to-date in Japan. "Japan’s History Textbook System: Creation, Screening, and Selection | Nippon.com" can be also used as the explanation of all subjects in Japanese primary and secondary schools.
In such a situation, what Japanese schools teach is very easy to research, different from what other countries do.
Wikibooks is a sister project of Wikipedia by Wikimedia Foundation. And its Japanese version has a project of Japanese schools' educational contents including textbooks by neutralizing real screened ones.
Such textbooks aren't used in actual classes. But you can check what Japanese schools teach roughly by that. And reading it makes your research much easier since you can find which grade's textbooks to check by the net.
Textbooks | Reference Guide | National Diet Library shows which library keeps the old textbooks. You can check the latest textbooks in Textbook Centers, in the libraries of national universities with education schools, and so on.
List of the Books in the Library of Osaka Prefectual Education Center is convenient to find the title of the screened textbooks since it's listed by subjects on the net.
And you can find the additional knowledges based on the screened textbooks by their publishers' websites.
In Japan, the textbooks are center of the educational contents. But they are often very rough. It doesn't mean that our primary and secondary education is so poor. You need to read also the reference books used with the textbooks and kids study books along the governmental guideline.
The contents of such books and of the web contents for pupils are written for the advantage of the entrance exams to middle schools, to senior schools, and to colleges. So their views are standardized although they tend to be leftistic.
You can find the most popular kids study books in the kids corner of public libraries.
There are some big kids learning manga series including ones with Doraemon, with Detective Conan, and with Crayon Shinchan. They teach various things to children in Japanese.