For me this job is something I do on a regular basis. I try to clean up the mail and file it in the morning while I'm in my room and the kids are cleaning their rooms. So it all gets filed away then, if it's a normal day. School stuff gets filed away as soon as it's done.
A thorough cleaning of the office filing cabinet happens during tax season when I take everything from the past year out and sort it and put the things that need to be saved in a small box in my closet. I buy my boxes for this in the office section at Wal-mart. This way they are stackable. I buy two each year - one for personal and one for dh's business. Once we have seven for each, then we won't be buying anymore.
A thorough cleaning of the school stuff happens during summer, when I'm getting next year's school plans ready. Each quarter we go through each child's folder and save one or two pages from that quarter. This goes in their memory box.
Doing as you go works super well, but I'm always finding piles of paper that need to be sorted. Such is life in my house.
Making the most of today
P.S. The in-laws are arriving tonight so we'll be skipping a few days probably. Enjoy the break.