For large lecture classes (100+ people), my university (professors/TAs) would post grades on the wall outside the lecture hall. For "privacy", instead of names

For large lecture classes (100+ people), my university (professors/TAs) would post grades on the wall outside the lecture hall. For "privacy", instead of names they used SSNs. Given the construction of SSNs (first five digits are a key for state-and-date), and our large population of students from different states, reconciling SSN to human was trivial. Ironically, the foreign students were in better shape because the registrar issued them an ID number which was not their SSN.