Even Their Mistakes Will Change

  • Even Their Mistakes Will Change

    By Juli Dixon, posted September 28, 2015 –

    Teaching mathematics based on rigorous, focused, and coherent standards requires teachers to know mathematics in ways that are likely different from how they were taught. Such teaching requires an understanding of the mathematics taught but also the mathematics that comes before and after that content so that appropriate connections can be established. Teaching for depth often necessitates a shift in how we teach, what we teach, and what we look for in student work.

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    This is less likely. This error is the type that teachers with a deep understanding of mathematics for teaching might anticipate. When mathematics is taught for depth of understanding, so that concepts are addressed before procedures are introduced, even student errors will be different. Teaching for depth does not necessarily eradicate errors. However, it does change them.

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    How might this problem be addressed when teaching for understanding? It would likely be introduced either in context or with an expectation that students develop a context to bring meaning to the problem. Think of a context before reading further. How does your word problem compare to the one provided here?

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    Once this error is identified, it is easily resolved. However, unless teachers have a deep understanding of mathematics for teaching, errors such as this will go unnoticed as common errors. What are other “new common errors” teachers need to anticipate? Discussion of common errors should be part of the process of planning for instruction so that the errors—both new and old—can be identified and addressed during instruction. In this way, errors become springboards for learning rather than long-term issues in building understanding.

    Anticipating common errors has always been an important part of planning, and teaching, mathematics. Now, knowing mathematics for teaching is more important than ever, including how misconceptions may appear as students persevere to make sense of mathematics. How are we as teachers and teacher leaders addressing the need to know elementary school mathematics with depth? What are we doing in teacher preparation, in school-based collaborative teams, and in professional development to address the need for deeper content knowledge for teaching elementary school mathematics? In what ways are we planning for a new set of common errors so that they can be addressed during instruction and through a formative assessment process? Until all teachers have this deep understanding of the mathematics they teach, all students will not have access to mathematics based on rigorous, focused, coherent standards.


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    Juli K. Dixon, Juli.dixon@ucf.edu, a professor of mathematics education at the University of Central Florida in Orlando, is interested in mathematics content knowledge for teaching as well as communicating and justifying mathematical ideas.

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    Ralph Connelly - 9/30/2015 10:40:14 AM
    This is a great example, and I love your clear explanation of how looking at the problem conceptually can result in the given error! The fractions chosen in your example brought back a memory for me, as I had used those same fractions in my math methods class when asking the students--"If you can multiply two fractions by multiplying the numerators and multiplying the denominators, do you think you could divide two fractions by dividing the numerators and dividing the denominators?" The students were almost unanimous in believing that this method would NOT work, and were quite surprised when in this given example, it did indeed give the correct answer (11/6 divided by 1/3, dividing numerators you get 11, dividing denominators you get 2, or 11/2. Doing other examples led to the conclusion that the method was "messy" unless the denominators were the same or related, but that indeed it was a legitimate algorithm, and a further discussion of what my students came to know as my favorite and inevitable question---"Why?" :)