I agree with having him circle the sign. Another way that might be fun is to have him use a highlighter and highlight all the signs first (use one color for add and one color for subtract), then do all the problems. He might like doing flash cards instead of "a sheet" and you could buy or make a set with different colors for add and subtract. Lastly, I might suggest asking him to check his work when done...if you add, the answer is more than either number...if you subtract, the answer is less. That way he wouldn't actually have to calculate them all again to check, but just use his number sense. (I've taught grades 5, 6 and been elementary math support teacher, but now am a SAHM to a four year old and 20 month old.) H.