As a teacher, I know that students hate studying grammar. While I can’t say I don’t understand this attitude (after all, I remember being a student and thinking it was the most tedious and complicated thing ever), I believe that this hatred is based on a misunderstanding of the purpose of grammar.
Grammar was not, counter to popular belief, invented to torture and confuse students. Rather, the purpose of grammar is to provide a common set of standards for communication and for the organization of words. Quite simply, grammar is the rules for the game that is language. Being a grammar ninja means that you have become a master of those rules.