Say I have a database of students, each with a unique ID, GPA, placement test scores, and some demographic information (nothing personally identifiable). The ID is generated using a one-way cryptographic hash function that produces a string based on personally identifiable information. With this function, it is theoretically* impossible to figure out the original data, but it still preserves uniqueness. This is typically how passwords are stored; industry standard stuff.
Does FERPA protect the release of educational records completely, or only when in combination with personally identifiable information?
* theoretically. the development of quantum computing notwithstanding, the Sun will die long before anyone can figure the original data by testing every possible combination of letters and punctuation of unknown length. See: https://en.wikipedia.org/wiki/Cryptographic_hash_function
[snip detailed example]