Mine have. Way back in 2nd or 3rd grade, we had to write stories using spelling words we had learned that week. One night I wrote mine (I think it had something to do with deer and vampires, don’t quite remember) and I made the mistake of leaving it on my bed when I left the room. When I came back, one of the dogs had apparently found their way in and ripped it to shreds. This was when they were both puppies, at that wondrous stage when they would chew up anything. Luckily I was happy to just write another story, but remembering this today got me wondering if the age old excuse has actually applied to anyone else.
Hasn’t happened to me, but I have to ask whether you took in the shredded up documents to class just to show off? 
Well, no, my parents made me throw the remains away while my brother laughed at me incessantly. It would have stunk up my bag anyway. I did tell my friends all about it though! 
Not homework from school, but a couple of months ago I was printing out meeting reminder cards for our next booster club meeting. The paper-catcher on my printer isn’t very good, and often the paper will sail right across it and hit the floor. The 5-toed chair sloth chewed the corners off several of the pages of cardstock before I got back.
Something is weird about that cat and paper. She trashed an entire box of Kleenex once.
The goat ate my friend’s essay (university homework). Does that count?
Actually yes and I did bring the slobbery bits as evidence.
My homework was way up on a counter, resting and being excited to be my homework. When my big dumb great dane reached up and knocked it off. Then the little black dog chewed it to tiny bits.
I always knew the little one was getting the big one to do his bidding.
No, but he did knock over the Christmas tree many years ago, chew up the pipe my wife had wrapped for me, tear up two stockings that were for the dog and cat, ripped open a bag of catnip, whereupon both animals got stoned silly. I came home to a dog frantically trying to get outside before spraying shit to the four corners of the house, and a cat that was moaning pitiably under the sofa for three days.
Well, sort of the opposite:
My husband is a middle school teacher. One day, he left a pile of grading unattended, and Spot the Wonderpup made off with one of the papers and chewed it to shreds.
So my husband actually had to tell a kid, “I’m sorry, but the dog ate your homework.”
Not quite. But my friend’s dog did leave dirty doggy footprints over a poster I had just finished for homework.
Green Bean - 
My rat once made my exercise book into a nest.
The fact that I left the exercise book strategically propped against the cage, and that I hadn’t actually done the homework in the devastated book I proudly showed the teacher next day, is not pertinent to the case.
Checking through work submitted by students for an Ofsted inspection, I did find note saying that some of the work was missing as the dog had eaten it…best thing was the inclusion of a photo of the ‘culprit’.
Very unfairly, I decided to remove both the note and the photo, on the grounds that Ofsted might not appreciate the humour!
My cat did once chew a corner of a job application I’d done, and left muddy footprints on it…
One of my cats did chew up a homework assignment once. It wasn’t too bad, but it wasn’t really all that presentable either. Luckily (I suppose) it was an essay that I’d typed up on the computer, but I didn’t have time to reprint it before going to school. So I handed in the chewed and shredded paper, and at the same time simply told the teacher that I’d bring in another copy the next morning. She agreed, and it didn’t really affect my grade or anything. Just bad luck.
I also did have a “printer ran out of ink” excuse too - but again, it was easy to prove because the pages I had been able to print (about 8 or 10 I think) had gradually become lighter and lighter and nearly impossible to read. Again, a quick chat with the professor gave me the leeway to just bring in another copy that afternoon or the following morning, depending pretty much only on my ability to get a computer at the library during a busy end-of-semester time! He was very understanding, if a bit joking at me because of the somewhat clichéd excuse.
No, since I never had one.
But my little brother once drew all over my composition :smack:
Not my homework really, but something similar. When I was in third grade, we had to learn flutophone. If you’re unfamiliar with them, they’re kind of like recorders. Once, I left mine unattended and… well, it was still playable, but it was not good.
On the bright side, I got to get a new one, and the colour of the new one was much prettier (what you got was random).
My dogs have never eaten my homework … but one of them once pissed on my carelessly-placed math homework (and my brown-bag lunch :chunks:).
Way back in the early 1980s, I turned in a research paper on the international law of chemical weaponry for my Int’l Law college class.
I got an A & when I asked if I could have the paper back, the professor apologized as, in his apartment building, a neighbor’s dog got into his apartment & ate the essay among several others.
Me: “Now Dr. German, if I’d told you that a dog ate my homework, would you have accepted that excuse?”
Dr G: “L No, not really.”
Not eaten, but I had a big project due for Physics in high school, and the muddy dog walked all over it.
Yep. And I brought the puppy and the shredded homework worksheets in a baggie to school (dad took the puppy home right after the teacher had a good laugh, of course).
Zap, my 4.5 year old aussie, made off with a student paper once, while I was grading. She tore it to SHREDS. I, too, had to explain to a student that my dog ate his homework. Fuuuuun. The student was kind enough to print out another copy for me. 
You don’t understand…Chunks is my dog!
…I once knew a guy who had a father 9who was a mail delivery man). All of a sudden, a house on his route began complaining that their mail wasn’t being delivered-so the Post Office did an investigation. Turns out, the letter carrier would drop the mail into a mail slot 9in the front door). The dog inside would then shred and eat the mail!