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Michael Doyle, a science teacher, has posted a critique of calculator use in math class on his blog.
See this is interesting, because I have a strong number sense and I never grew up with an abacus.
I did spend hours and hours playing with numbers with my calculator. I would add/subtract/multiply/divide them and look for patterns. I was able to look for patterns into big, big numbers, because the speed at which I could calculate wasn’t limited by the tool I was using.
What’s missing from current instruction is actual time using the calculator to play around and construct one’s own notion of numbers. Just like you want kids "doing science" they don’t get enough time "doing math." The calculations are not the math, anymore than the list of content expected by your state curriculum in science is the science.
There is not enough time spent ensuring kids understand concepts, and too much time kids "cover a broad curriculum."
The issue is not the technology being used to do the calculations, as the abacus is a visual & kinesthetic tool, while the same holds true of the calculator (you do have to press the buttons after all). The issue is that students do not get enough time in math do more than memorize rote facts, and almost never get exploration time.