Oh, geez. This was me several years ago. My oldest is now a 7th-grader, but I homeschooled for 1st and then kept a goodly chunk of work through 3rd.
Then my mother-in-law moved and de-cluttered a ton of my husband's elementary-level work on us. We were swimming in her cast-off memories for weeks and he was very resentfull and left most of it for me to resolve.
Realizing how very little ANY of it meant to him, I woke up.
Your son will likely NEVER have any warm and fuzzy feelings over his 5th grade art projects and certainly will never fondly leaf through his old multiplication work.
Pull out anything worth framing -- seriously. If you are not willing to spend a certain dollar amount, say $50, on it to have it framed and hung appropriately, then chuck it.
As for the academic stuff, keep his report cards in a slim binder or file and recycle the rest.