A pass that expires by itself
A visitor credential is a QR code valid for a defined window, read at the same lane as staff. Nothing is handed over, so nothing has to be chased at the end of the day, and no unaccounted badge leaves the site.
Contractors, peripatetic teachers, exam invigilators and parents all pass under the same rule, and the record of who was inside is created at the door rather than reconstructed from a book afterwards.