In case a student is transferred to another class you may want to hide that
student from a specific tab.
Hiding a single studentFrom the grade book view, tap&hold on a student and Hide
Hide a group of studentsTap on tools (top bar) / Students / Select your students and Hide
Un-hide a studentTap on tools (top bar) / Students
Here you may either select a group of students, and tap on unhide
or you can directly tap on the eye icon next to each hidden student.