Using a Portal:
You could setup a portal filter with an expression that refers to a date in either a global field or a field defined in Students. Enter a date in this field, update the window's display of the data and only the attendance record for that student for that date should show in the portal.
or without a portal needed:
you can define a different relationship to a different table occurrence of Attendance_Log where an additional field in student specifies the desired date so that this relationship matches by student ID AND by date.
Using a calculation:
ExecuteSQL (if you have FileMaker 12 or newer) could return the desired data by specifying the Student ID in a join clause and the specified date in a WHERE clause.
If ( Attendance_Log::Date ="Sept 1" ; yes ; no )
Just a note of caution, "Sept 1" is NOT a date. It's text and should not equal any value of Attendance_Log::Date as Date should store and actual date value, not text.
but this calculation fails because the result only represents the result of the search of the last matching record
Actually, the calculation will refer only to the Date field of the FIRST related record. (Portal sort orders, Filters do not affect which related record is first.)