Correspondence and Pupil Report tick boxes
The Parental Correspondence and Pupil Report flags on a contact should be set for those parents who do not live with the student and who wish to receive correspondence and/or a copy of the pupil report.
You can then produce labels/reports that include contacts that have these boxes selected. A filter could be added to this.
It will also allow you to produce labels etc for split parents so the letters go to both.