In addition to all the great advice above, use fine sand paper to finger spell the words, and if the teacher will humor you, have the sand paper available to spell out finger style first on the day of the test.
You can also ask for accommodations if you're on an IEP (sorry - don't remember) - spell verbally instead of written, given less words each week, no word searches as homework - to name a few.
But for us, it didn't matter how much we practiced or how he tried to learn the words, he could have them all correct the night before the test and still get a 30% when he took the test. I finally stopped making him spend hours practicing for a test he would likely fail and used that homework time to do something more productive. In fourth grade, he studied every night and got F's. In 5th grade, we never reviewed the words at all, and he got F's. he felt better about those grades, because he didn't feel like a failure. And little by little as he gets older, a few words are starting to click.
So my advice is to try them all, and if something works, embrace it. If it all fails to produce amazing results, just make sure your kiddo knows life will go on without being a master speller.
