I think there is a problem with checking past students attendance in this lesson. There will be incorrect information if there are two different classes take place on the same day.

To see if this is the case, do the following:

Make this simple. Modify the tables so that there are only two students: CustomerID 3 and 2. (Fig 1)

Notice that CustomerID 3 was enrolled in ClassID 1 while CustomerID 2 was enrolled in ClassID 4.

Now open ClassF form and change the date under Take/Check Attendance button to 7/4/2022 (Fig 2)

Click the Take/Check attendance button

Notice that there are now two students in the list. This is incorrect. ABS inc wasn't enrolled in ClassID 1. He was enrolled in ClassID 4.

The problem lies on the subform inside AttendanceF. The subform uses AttendanceByDateQ query. (Fig 3)

The AttendanceDateTime field in the query is restricted by [Forms]![AttendanceF]![CurrentDate]. But this is not a good enough restriction since this only restricts the date but not the class. To restrict the class, the ClassID field must be restricted by [Forms]![AttendanceF]![ClassID] (Fig 4)