Although students may have multiple assignments in a day, teachers, especially at the secondary level where they have six classes, could potentially have as many as 200 assignments on a single day. It is not realistic to think that any teacher has the time during the day to grade and update grades. More often than not teachers grade papers during their free time in the evenings, on weekends, at their children's events, etc.
Updating grades weekly is a more realistic standard.
