I'd find something definitive like in an editor's book of ____ (sorry, I'm not an editor so I don't know the names of what you'd use!) - ie, something official and not to be argued with. I'd show that to my dd, and have my dd take the paper in with the book reference and explain it to the teacher. She can let the teacher know that her mom's a writer and an editor and that she was following her mom's direction in not capitalizing, and ask that the teacher reconsider her grade. If she was younger, I'd make that call to the teacher myself, but I think that by 5th grade most children are able to begin to advocate for themselves in small ways such as this. If the teacher still doesn't relent or disagrees or generally gives your dd a hard time over it, I'd follow up with an email.
The reason I'd have my dd do it is that a) it's a good opportunity for your dd to learn how to advocate for herself and b) I think the teacher will be less likely to be put off or annoyed if the student asks for reconsideration rather than just the parent.
OTOH, take that all with a grain of salt - my kids have always attended schools that are big into self-advocacy - it might not be the same elsewhere.
Good luck!
polarbear
