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Saturday, October 11, 2014

13 Rules That Expire

Today I happened to find a must read article for all math teachers that really resonated with me called "13 Rules That Expire" by Karp, Bush and Dougherty in Teaching Children Mathematics.

There are just too many things that are overgeneralized in classrooms and the authors do a great job of not only pointing out some of the misconceptions that we allow students to use, but also how quickly they expire. Here's one that has been my little pet peeve for a while: the equal sign means find the answer or the answer is. This little misconception should be expiring in first grade, but I'm not sure older students understand the correct meaning of the equal sign. Change your language to "two plus two is the same as four" to help students understand that the equal sign represents a relationship not an answer.

More misconceptions:
  • when multiplying by ten, just add a zero
  • you can't subtract a bigger number from a smaller number
  • use keywords to solve story problems
  • addition and multiplication make numbers bigger
  • two negatives make a positive

If any of these are things you've taught, you'll want to read this article. There are more overgeneralized rules, plus suggestions for alternative language to help your students. Click on the link above to download the article from the NCTM website. Plus, the authors ask for more examples of rules to expire to keep the conversation going on the NCTM blog. So think about sending in some of your own examples.


  1. This is a wonderful article and every teacher of elementary aged children should be required to read and memorize it. I have published many, many guides for teachers that demolish each of these misconceptions over and over again, yet I still visit classrooms where teachers state these same rules over and over again.