There are 200 Kanji in Japanese School Grade-4. Kanji list starts from 441 till 640. Just browse thru previous and next in the above button. In the URL HTML filename, you can enter a number between 1 to 1006 to directly jump to a Kanji. For example to access first Kanji the filename is, "school-grade-kanji-1.html". In this, you can change the number "1" (to the desired number) before the ".html" to access a Kanji.
OnYomi reading of the Kanji is used when the Kanji appears as part of a compound Kanji word.
KunYomi reading is used when the Kanji appears alone in a statement.