I tried this and submitted a piece of my teens writing and I love it! It was really helpful getting feedback and information that wasn't coming from me, MOM.
The report that came back examined the following; Plagiarism, Spelling and Grammar, Style and Word Choice Analysis, Readability Statistics, Title Validation, Vocabulary and also graded the paper.
I really liked how I could read this over to my teen for a more "objective" point of view. Let's face it us Mom's who play Editor have a tough job critiqing our learners work and its just nice for us to have something that we can use to give feedback that is constructive and can be used as a great teaching tool.
I hope you get a chance to give this a try~ If you do let me know what you think!