How to insert an attribute and value 'true' to a record and false to remaining records and records in other tables?

I have list of tables class1, class2, class3...Each has multiple records like department, student, subjects etc.

Student records have attributes USN, branch, age, DOB, phoneNo, isLeader, isPresidentisLeader = true if student is a class representativeisPresident = true if student is a President for student union

If I insert isPresident = true for one student from one class(table), all student records should be false(even from other classes because there are multiple classes, but studenti president is unique)

Once I insert isLeader = true to one record, other table/tables'isLeader values should be changed to 'false'.

I'm using dynamoDB, lambda function with Python for coding.