One register, and everything else reads from it. Attendance, marks, fees and messaging all resolve to the same student record, which is why it has to be right before anything else is worth doing.
The whole family, not just the child
Guardian name, relation, phone and email sit on the record, because every message the school sends goes to a parent rather than to a student. A sibling in another class is on the same family, which is what makes a sibling concession possible.
The fields a government return asks for
Category, caste, religion, mother tongue, Aadhaar, date and place of birth, nationality and a full address including district and taluka. These are held as fields on the record rather than as free text, so a return can be filtered rather than read.
Photographs and documents
A photograph and the documents collected at admission stay attached to the student, so a report card or a transfer certificate can be produced without a hunt through a cupboard.