Ancient language, modern grammar
One of the unfortunate facts about studying English at a grammar or high school level for native speakers is the absence of true study. As the brilliant Professor Higgins, as played by Rex Harrison, stated "the English are not taught their own language." As native speakers, many cannot explain exactly why some form of grammar is correct, beyond "It sounds right." It is true that most of the time when something sounds right, then it is likely grammatically correct, but that still does not explain why. The hardship comes in trying to explain to non-native speakers why or how some form of grammar is appropriate or not. There is however a growing number of people of native English speakers who have begun to understand the way their grammar and language functions. Not through the study of English, but through the study of Latin and Greek. Both of these languages are inflected, meaning that placement and function of the word comes from the ending. Because Latin and Greek, at least the authors that are most commonly studied, have complex and varied grammar, the student then begins to learn the grammar of English while working a translation. Maybe more students should be learning ancient languages. I can honestly say, that it was Latin and Greek professors who taught me how to explain and understand English grammar.