We keep financial records, but not something like a survey. For us, either the information was short term and obsolete or it's been summarized in a computer file.

We wouldn't keep paper copies at all.

Last year we did a survey for the parents and I still have the papers. Storage is a problem and half of the families have either moved away or transfered to other schools so most of the info is no longer valid.
So, how long should we keep them?