I have found a solution. First time when creating or adding a new student to class (NSManaged)object in class (NSManaged)Context, also add a new instance of Score (NSManaged)object having newly created or added student in its relationship and at the same time assign them default '0' value to all other attributes.
Later you can reassign values depending upon situation.
[student setValue:@"Beckham" forKey:@"lastName"];
[student setValue:@"Soccer" forKey:@"belongsToClass"];
after this new student has been added keep a reference to it and use it in new Score object as-
Score *score = [NSEntityDescription insertNewObjectForEntityForName:@"Score" inManagedObjectContext:managedObjectContext];
score setValue:[NSNumber numberWithInteger:0] forKey:@"dribbling"];//attribute
[associatedScore setValue:[self newlyAddedStudent] forKey:@"belogsToStudent"];//relation
Thats it.