The Educational Structure of the Japanese School System - Detailed info as far as statistics go. Covers cram schools as well as elementary, middle, high, technical schools, and universities.
Schools - General info.
Kids' Life - A few links to pages on life in individual schools. Ranges from elementary to high school.
Semi-related: Traditional Japanese Toys and Games - Info on various low-tech childrens' games.
Hope it's of use to someone else.