If there isn't a teacher, make up one as an NPC. That's all I can say. As far as how everyday class would go . . . You'd have your basic, everyday school classes, like some form of math, language arts, science, physical education, etc., then on top of those, you have your elected Summoning Course and a Strategy Course, the latter of which is where characters are tested through Duel Puzzles, Decks built with specific strategies that must beat another, or simply testing their Decks against each other. There may be free periods here or there throughout the day, including the designated lunch break at 11:45 that melds with a free period until 12:45.