In the very beginning I did (kindergarten) then I went through at the end of the year and got rid of all but the best, mainly art and writing assignments. Then the next year, not so much saved, continually pruning the mountain of paper!
When I began homeschooling, that "save everything" started all over again.
But now, I am back to the point, of only saving the best: projects they did their best on, art projects, higher level exams, book reports, poetry, things that are sentimental or relevant to a portfolio.
I think you are doing enough, but you may want to hang on to some examples of writing assignments and other projects for a portfolio.

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