I remember when my kids did the invented spelling in first grade - I couldn't even figure out the subject of the writing piece. However, by third grade all were good spellers. DD18 is one of those people that just "gets" spelling - she very rarely makes a mistake and almost never cracks open a dictionary. DD16 is a good speller but makes a mistake once in a while (typically on a difficult, commonly misspelled word, and she usually realizes and looks it up). DD9 is similar to DD16.
I'm not certain how they made the leap from invented spelling to correct spelling. It may have something to do with attending a French immersion school from Pre-K through early elementary. While invented spelling is tolerated in English, it is not in French. Perhaps the push for proper spelling, grammar, etc. in French may have had a positive effect on the English.
