Big sigh... Did you catch the discussion around Christmas on this board on Math vs Wordy kids?
A differentiated spelling list seems to be called for at least.
My daughter's school started a differentiated spelling program this year - 3 lists per class basically. All the lists are about the same letter pattern like ch, sh, or whatever. It seems like a pretty easy system to establish - the kids actually dictate the spelling tests to each other so it really is no more work...
I can't say anymore without groaning...
chrys