Can this be done by triggering a "Canceled" setting for all student attendance upon clicking the "Class canceled" check box? Saving the attendance dialog with the default "Attended Class" after one checks the "Class canceled" box is not intuitive, nor is it logical.

This would prevent confusion about who is on campus and who is not.

I agree! This would be helpful for attendance managers at our school as well. We have students who have schedule conflicts and can be potentially enrolled in 2+ classes/clubs/labs the same period. Having it look like a student attended when the class was actually canceled creates more work on the attendance manager, who then has to click into the individual teacher's attendance list each time to see if the attendance was taken (and the student was present) or if the teacher canceled (and the student was missing in action that period).

This would also be helpful to the student in the event that the teacher has not announced this in advance.