This option is used to assign a new teacher in an existing course period. It can be used in various scenarios such as teacher leaves the school or will be unavailable for a definite duration or any other administrative reasons. To reassign a new teacher in an existing course period go to School Setup >> Courses >>Teacher Re Assignment. Now, select the subject, Course and Course period in which the change is needed. Then, select the new teacher you want to schedule in the selected course period from the "Select New Teacher" dropdown menu & assign a date (the date from when the new teacher will be teaching the selected course period) and Save the changes.
From the given date onwards the previous teacher will lose access to their portal (in case of teacher dropping from the school), else, will not have access to that course period in their portal, since the new re-assigned teacher will take over the class and access to the assignments, attendance records and final grades, given by the previous teacher.