Archetypes exist. Certain plot lines are often used (e.g.: Boy meets girl, boy loses girl, boy gets girl). It might be original to you but merely a remix to someone else who has read a lot of stories. Star Wars has a lot of elements found in westerns. Harry Potter has two talented companions just as Kirk has Spock and McCoy or the Doctor has Amy and Rory. Just look at how many scripts from The Honeymooners were rehashed for The Flintstones and The Jetsons. (Apologies to the writers if the script was taken from the cartoon and rehashed by Jackie Gleason and the other cartoon.)

Don't give your ideas away you teacher will steal it ;)

Any teacher that accuses students of plagiarism had best be able to back it up with solid proof. I would definitely demand an explanation and bring your writing. And if you don't get satisfaction from that, take it higher to the principal. You deserve credit for what you did, you don't want your teacher to think you would do such a thing (it will him/her to be biased against future work most likely), for other students' sakes you need to hold this teacher accountable so they don't ever take thd charge of plagiarism lightly again. Speak up!

Show him what you have written, and if that isn't enough proof... Ask to see the actual myth!

Hey I have a few questions. 1) Do you go to wentzville middle 2) Are you in 7th grade and 3) Have Miss. Mogerman as your com. arts teacher

my brother had a teacher outright accuse him of plagiarism because a short story was really good. It happens.

...Chuck Shurley??

I have to write a myth in my English class. "due two weeks ago"

That doesn't make it original.

I've always been paranoid of writing something that someone else already wrote by pure coincidence and being accused of plagiarism.