Of the four words that you listed, technique is the only one that gives me pause; the other three words would have fit in with what my kids were covering in their stand-alone pseudo-GT 2nd grade Reading/Language Arts, which typically worked about a year ahead. Whether he has to work harder than the other kids really depends on his spelling ability compared to the other kids' spelling abilities. In my opinion, even "practicing" 5-10 minutes a day seem a bit much, as I assume that the teacher assigns some spelling homework like alphabetical order and making sentences, which already reinforce those words. My kids never practiced spelling except on rare occasions with one or two words missed on the pre-test and there were always a fair number of classmates who also didn't need to study beyond the spelling assignments. To be honest, I am alarmed that practicing 20-30 minutes a day is even a possibility. I would tell him that you don't care how he does on the test as long as he just try and that you are limiting his practice to 10 minutes (or less) a day.
