Personally Identifiable Information under FERPA
FERPA's PII definition covers names, family member names, addresses, SSNs and student numbers, dates and places of birth, and any information that alone or in combination could identify the student with reasonable certainty - and it can overlap with directory information.
The Department of Education's definition of PII includes the student's name, the name of a parent or other family members, the student's or family's address, personal identifiers such as Social Security number or student number, other identifiers such as date and place of birth, and any other information that alone or in combination can be linked to a student to identify them with reasonable certainty. It also covers information requested by someone the school reasonably believes knows the student's identity.
FERPA's PII can overlap with directory information - for example date of birth and place of birth fall into both categories. The categories are handled differently for disclosure purposes, so practitioners must track which rule applies.