Workspace in a School: How to automate the detection of a utent's membership in more than one group

[zivug]

The educational institution includes multiple schools and therefore multiple plexuses (primary and secondary).
It is organized by groups and organizational units the class membership of pupils; if a John Doe pupil belongs to class "1 a" in elementary school, the relevant organizational unit will be: main school name>primary school name>1A (class name).
In addition, there exists for that class a group in which the same pupil will appear to belong; for the example from before: John Doe will belong to the group: "elementary school name 1A."
Since there are some pupils who, for reasons due to the change of the managing operator, have been mistakenly added to more than one class and thus to more than one group, I wonder how it is possible to automate the way to scout them out and delete the membership of the groups to which they have been mistakenly added without manually examining the membership one by one of the same.