Now I'm confused. Are you saying that if I waive my right to see the letter, and you write a candid letter based on that waiver, that I could still request access to the letter via a FERPA request to any school that receives it?
I have not seen anyone do a FERPA waiver with a submitted letter. I'm not saying it doesn't happen, but for those of us writing them it is not common practice.
With committee letters, we have students waive the right to access the letters our committee receives and stores: those are part of the educational records at our school.
Similarly, faculty need a signed FERPA
release to write a letter- this is the student authorizing permission for a faculty member to share information from their educational record outside of the school (to employers, graduate programs, etc.)
For letters going through centralized processes (such as AMCAS), the waiver is part of the AMCAS or ACOMAS system. For instance, when I get a letter request through Liason (for dental school or DO programs or such), it tells me as a letter writer whether the person requesting it has waived their right to view the letter or not before I submit. That waiver then goes to schools along with the letter.
For things like post-bac and graduate programs where letters often go straight to a school, the school receiving the letter asks the student to waive (or not waive) their right, and communicates that to the student.
Essentially, the waiver is tied to the recipient of the letter, not the writer, as it's part of the educational records at the school the student is applying to.
It's an (increasingly complex) process for letter writers and institutions to keep track of- as
LizzyM says, some schools response is to ensure they don't keep letters as part of educational records, which means they cannot be requested. And yes, it's certainly the case that when I'm sending letters (e.g., for grad school) to 10 or 12 individual schools, a student could try to game the system by not waiving their rights at one school to try to see it, and the writer needs to review the submission portal for each time they submit the letter.