If ADDING pupils to sets manually.
You need to have a warning which shows if a Pupil is already in another set in the same 'department' or the same 'subject'. Nothing to avoid you adding Pupils to a bunch of sets when they already appear in another class within that same Subject
For example with a timetable column change.
You should have a 'this pupil is already in S5ENCol1'
'do you want to add them to 'S5ENCol2 and remove them from S5ENCol1'
even when you 'MOVE' pupils in Teaching Manager Pupil View you have no way to see which line you've definitely clicked once it has been click so a warning of possible duplicates would be useful.
(grey highlight would be helpful in Teaching Manager Pupil View to confirm which line you are on).