Truth is, there is no absolute standard of correctness in grammar. Never has been. The notion of absolute correctness comes from a combination of strange Biblical interpretations mixed with the "golden age" hypothesis. In the 19th century, it was widely believed that the language spoken in the Garden of Eden was Hebrew (though why anyone in his/her right mind would think that is beyond me). All languages were descended from Hebrew and were corrupt forms thereof (see "Babel, Tower of"). English in particular was a degenerate form of Latin, and if Latin had an ablative, then English must have one too. The "Golden Age" of language was the aforementioned garden, and things have been going downhill since, which they continue to do.
Because of this and some rather pernicious inventions (two negatives make a positive), there is a great deal of nonsense taught in the school systems about what one should or should not do in writing. For instance (and all of these are ridiculous rules):
- Never begin a sentence with "because"
- Never begin a sentence with "and" or "but"
- If you outline and you have an "A," you've got to have a "B"
Bah! And humbug! But you may not believe me. Because of this, you'll continue to fret over things that are not only non-essential, but not really real except in the minds of English teachers, who should find better things to do with their time.