During the development of St. Rapahel's faculty handbook, I researched a similar topic. Through my research we were suppose to retain student documents (transcripts, test scores, etc.) for three years following their departure. Sadly, I cannot remember where I found that particular information.
I am not sure how our secretary keeps it organized or how FERPA fits in.
I did a little research on this question a few years back and have attached the report I wrote at the time. The student records at the time were pre-digital, so the driving force for research was storage and space. I found my local public school administrator-peers to be a very knowledgable source of information on this topic.