How I Use It
I would use this at the beginning of the year to quickly review the parts of speech. I would have students complete each of the three levels of difficulty until they could do so without any errors. The site also proved an elapsed time after the round is completed. Students would be encouraged to beat the teacher.
After introducing this game to students, I wonder if they could fashion their own Grammar Ninja games with sticky notes and white boards for subsequent grammar concepts.
Grammar Ninja sounded like a tool that would review several aspects of grammar. I wish it offered comma rules or at least independent/dependent clause identification. As far as I can tell, it just does parts of speech. It does provide three levels of difficulty, though.
I liked that the site offers helpful clues/definitions to the students. I also like that the time commitment is minimal.
It could be used as a quick formative assessment if your level requires mastery of this grammar concept.