Is it possible to mark a student as tardy / late for class?

Yes, when you are using the Attendance feature in the Staff Portal you can track when students are late, leave early, or are just observing class. 

Watch a (1:42) video tutorial on Tracking Late, Left Early, or Observing

For students who are marked present in the Staff Portal, you have the option of adding attendance details noting whether the student was late for class, left class early, or was just observing class that day.

Use the arrow next to the Present button to drop down the attendance detail options; select all that apply.

For each option chosen, a badge will display under the Present button.

Report on the attendance details using the Student Attendance Report

It is not possible to track late, left early, or observing if you are marking absences and attendance in the database directly; these details are only available for Staff Portal Attendance.