One of the significant problems with digital portfolios is that the work has to be in a digital format. That works well in most content areas, but in one like math, it poses a problem. Another issue is the time and effort it takes to digitize the work itself. I believe it's vital for most of that legwork falls upon the student. That way they are learning how to digitize analog (if I can call it that) work, and are responsible for owning their portfolios.
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