The Reflective Educator

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A math question

I’m working on a system where students will be able to post their non-digital work directly from a scanning station to their eportfolio blog. I want to make the system simple enough that young kids can potentially use it themselves (and ask our teachers to review the portfolios of our students periodically). To this end, instead of asking our students to enter a user name and password, I’m considering asking them to just enter a 5 or 6 digit passcode made of numbers, letters, or a word (which would be recorded somewhere for easy access for the younger students).

What I hope to avoid are collisions where two codes are so similar that students end up accidentally posting to each other’s blogs (either different by only one digit, or by two digits being transposed). One thought I’ve had is that I can use a barcode or QR code scanner, but as this may be challenging to set up, I may need to use a simple passcode to begin with.

My question is, what is the minimum passcode I can use while minimizing the chance of a passcode collision for our nearly 500 students? I’ve done some work figuring this out for myself already, but I’m curious about some other approaches.