It’s not really a grading tool, but it might be worth introducing into the writing process. I’m running a paper workshop tomorrow… I might give it a shot.
PaperRater.com is a free resource, developed and maintained by
linguistics professionals and graduate students. PaperRater.com is used
by schools and universities in over 46 countries to help students
improve their writing.
PaperRater.com combines the power of natural language processing (NLP),
artificial intelligence (AI), machine learning, information retrieval
(IR), computational linguistics, data mining, and advanced pattern
matching (APM). We offer the most powerful writing tool available on the internet today.
Before we could offer PaperRater.com we had to overcome large
challenges related to computational linguistic design and development,
handling transliteration variation; ethnolinguistic identification;
document classification and entity extraction; name parsing and
regularization; duplicate document recognition, plagiarism detection,
clustering, and prioritization; automatic entity extraction and entity
resolution. —About PaperRater.com