Waou. That's a definitive answer, of course, but that's really time-consuming. Definitely an overkill to me.

I do this for exams (that are worth a substantial part of course grade), it doesn't take long. I don't bother for small assignments.

People were doing this even 25 years ago, but photocopying instead of scanning. Not overkill.

It's not time-consuming with an auto-feed scanner. Just put the pile of papers on it and press the button.

Scanning finals and midterms is a good idea because it's often possible for students to contest grades years later.

@ElizabethHenning Can you even do anything years later?

"That's a definitive answer, of course, but that's really time-consuming. Definitely an overkill to me." If you're having trouble with a student repeatedly pulling the trick, you can photocopy just their test. Then next time they do it, give them a zero for the course and report them to the administration (most universities have zero tolerance policies for cheating, in which the punishment is at least a zero for the course, if not expulsion).

@Clément It's really not time-consuming on any reasonable modern multifunction copier/scanner/printer. Dump the stack of assignments in the top, hit "scan", and let it churn through them at (usually) something like 30 pages per minute. A few minutes later you have a PDF on your USB stick or emailed to you, which you can ignore completely unless a student raises a dispute. The sheet feeder's automatic, so you can do something else while it's scanning.

I'm maniac enough to be willing to divide that big pdf into individual pdfs, and then storing them, and backuping them, in multiple way. I'm sure with a bit of organization you can do that pretty efficiently, I must agree. This just seems… a bit of an overkill. Also, it's not so modular: what if the student wrote on the back of the sheet? Added an extra sheet? But I'm sure it's a definitive answer to that problem (that I never met, actually).

@Clement Big multi-function copier/scanners will scan front and back of a sheet for you. The biggest problem would be people stapling or folding sheets.

We immediately stapled exams to reduce risk of lost/mixed up sheets - I think that risk also needs to be taken into account when discussing scanning as a solution.

@Clément If a student writes on the back of the sheet, that will be scanned too, provided the scanner was set to double-sided. If the student adds an extra sheet, that will be scanned too. The sheet-feeder doesn’t know how many sheets should theoretically be in the pile: it just works its way through the ones that are actually there. As others have pointed out, the most likely potential problem is stapling, although (as RLH mentions) slicing the corner off is a quick way to remedy this.

Totally the right answer; I've been doing this for years. Takes about 1 minute per class on any bulk feed copier/scanner at the school. (Perhaps you should edit the answer to specify, for those unaware, how quick this is?) I also design the test papers so there's always 1 sheet per person, no staples, etc.

I scan also, but I also allow PDF submissions for take home tests. Keeping the tests allows me to review the test later, when I write the next one. And at my institution, any grade is contestable, for a long time. Also, when there is any question of academic honesty, on my part, I scan all submitted work.

Evan a small office scanner such as the Fujitsu Scan Snap iX500 will scan (both sides at once) at 25 ppm, with a hopper of 50 sheets. Bought one recently for a home office and it's a world away from the process you'd need with a flatbed scanner, which is what might be what people are imagining. Just load the hopper and press the button on the scanner and it's done, with the scans saved automatically.

I do all the things mentioned in the answer and the comments, but still I think that many users are making it sound easier than it really is. I have 150 students, and I scan the quizzes. First, our photocopier/printer/scanner is nowhere as fast as suggested, and I don't think it scans more than 10 double sided pages per minute; it's actually slightly faster to scan each side separately. And then the feeder won't take all 150 sheets. And then the feeder will jam on one of the last pages, and the machine will discard the whole job. It can be done, but it's not pretty.

Although I prefer Clément's answer in most cases, I'd go with this one BUT not warn the students that scanning is happening. Then you'll catch a student in the lie, he might even confess, under pressure, that he got the idea from S2, who got the idea from S1 and you've taken care of the past.

@MartinArgerami: You have a bad scanner. I've been doing this for at least 4 years with every exam, on a variety of machines around my institution (a community college undergoing budget cuts) and it's never jammed or taken more than a minute per class.

@DanielR.Collins: either you teach very small classes, or you have some kind of magic scanner. I will have to see it to believe that any scanner can take 150 pages, double sided, in one minute; and that would have to include the two/three pile replacements, because again I doubt that any scanner takes a lot more than 50 pages on one batch. In any case, I cannot dispute that our scanner is slow (22.5 minutes to scan my quizzes today), but I don't have a say on it, as any purchase of individual printing equipment is banned in our campus.

This answer is good, but is totally outdated. Electronic submission is better for everyone. Why make students print out their work so you can have the task of scanning it?

@emory in maths and physics, most students write their assignments by hand. (Don't know why; I was always the oddball who TeXed everything and agree that electronic submission is better.)

I would suggest simply making a photograph instead scanning. Cheap mobile phone camera should do the trick – it doesn't need to be properly readable, just clear enough so it can be compared with the original.

@MartinArgerami: To be clear, I do have smaller classes than you're talking about, but likely more of them: 4 courses per semester with about 30 students each; so every test day, 120 pages, double sided. About 4 minutes to scan, no jams, no magic.

With modern smartphones resolution it should be quicker and more convenient to make photos

@PlasmaHH Unless they have a printer that scans by itself amazon.co.uk/Epson-GT-S85-Sheetfed-Scanner-40ppm/dp/B0060WC2‌​CQ

@PlasmaHH physically turning each page and lining up the camera to take a picture is faster than batch scanning? No way. I would guess using a camera would take three to four times longer. The average speed for CONSUMER batch scanners I see (in duplex mode) is 20-30 pages per minute. A commercial one should be faster. Plus, a lot of new ones have text recognition, so they can separate files by student or whatever you want.

@AytAyt: I agree with most things you say, with one exception: there's no computer in the world that can read the terrible way my students write their names in their exams.

@MartinArgerami HAHAHA that's probably true of my handwriting as well. I should have said "they SAY they can"

And how do you prove you didn't use MS Paint to erase answers or just did something very nasty?

@ΈρικΚωνσταντόπουλος I suspect a blockchain could solve that, but I think it is overkill.

@AytAyt it can be if there are problems with the document feeder. Do students let there dogs chew on them before turning them in?

Too tedious, too much work.