Scenario from my youngest kid (dual credit student):

Wrote a paper for a class in the fall and submitted but had to drop the class and move it to the Spring. Received no credit for the class. (When originally submitted it passed the plagiarize checker.)

Submitted the paper in the Spring for the same assignment and same class, just changed the date of the paper. Came back as 100% plagiarized, no kidding and you can deduce as to why. Professor says it stands after finally grading the papers in the class 3 weeks after the initial due date.

So, did my kid plagiarize?

Obviously she turned in the same paper and she fully admits to it.
Never received credit for the paper so in my opinion it was never "published."

Anyone ever run into this?

P.S.: This has a very huge implication for my kid as she sits at the top of her class in a very small school.

I taught in college and AP and Dual Credit English in high school.

One of the first things professors and teachers need to learn these days is how to correctly interpret plagiarism checkers. A little common sense goes a long way.

As you know, there is something called "self-plagiarizing" when you turn in the same essay for multiple classes and thus receive multiple credits for the same work.

The term also applies to publishing essentially the same work in different journals.

However, your daughter did not do either one.

She did not receive multiple credits.

She should not be penalized for turning in the same paper and receiving credit for it one time.

The professor is wrong. Appeal to the department head and then to the dean.

Depending on how things go and if you know the local ISD superintendent and/or members of the school board, escalate it and explore the possibility of ending the relationship with whatever college your local ISD is using for Dual Credit. I hope it would not go that far.

I would not call this plagiarism.

Some courses at some schools have an "originality requirement" that indicates that writing for the course must be original writing produced by the student for that class this semester. It might include that students should not recycle their own papers from previous courses. If the course syllabus does not include a requirement like this one, then look at the school's scholastic integrity policy. If the school's scholastic integrity policy does not address this specific issue, then I'd advise the student to appeal the decision.

If the student received a zero and it is for a scholastic integrity violation, the student should be able to appeal immediately, and the student will want to do so because there is often a time limit for appeals.

I encourage the student to review the syllabus, the assignment prompt, and the school's scholastic integrity policy, and if there is not an originality statement nor a "self-plagiarism" prohibitive statement, then the student should meet with the instructor (make an appointment or go to posted office hours) and kindly ask how the student could have known using the paper would not be allowed and go from there.

Personal note: if a student asks me about reusing work he/she has written for another course or another instance of our course, I will tell that student yes/no/with modifications depending on how the previous work fits our assignment. Asking the instructor about reusing work is the best way to avoid a penalty for reusing work. Also, in your student's situation, I would have my own child write a new essay that fits the assignment requirements and take that to the meeting with the instructor, so he could end the meeting with "well, I wanted to demonstrate to you that I am capable of producing another essay that fulfills this assignment. I hope you will read it and consider accepting it." I think this shows the student is willing to do the work and will do it even if he/she might not get credit for it.

let me guess: was the paper flagged by TurnItIt?

Here's more information:
https://www.turnitin.com/blog/what-is-self-plagiarism-and-what-does-it-have-to-do-with-academic-integrity

this YouTube might help:

It's 'not citing your sources'.

For academic papers to have merit, sources must be provided for fact checking and validation of research

I think we were on the right track in our approach after reading these responses, so thank you. Unfortunately the school will not allow access to how the checker works.

Fortunately though, the professor did not know or realize the student had previously dropped the class the prior semester and never received credit for the work. He allowed it to be graded, which greatly increased the grade.

In the end, this could have all been avoided if professor would have responded to communication from our kid.

Glad it worked out!