Number Line in grades K and 1

[noamszoke]

Hello,
We are wondering about the use of the number line as an instructional model in grades K and 1. The number line first appears in the CCSS-M in grade 2, in 2.MD.6. It is not mentioned in the progressions before then. Various sites use it extensively, while at least one (Arizona – https://www.azed.gov/azccrs/files/2013/11/kflipbookedited.pdf) exhorts against it.
What are your thoughts on this? There is a looong tradition of number line use in Kinder (e.g. Math Their Way, etc.) but is there research giving us direction on this?

thank you,

Noam

[Bill McCallum]

There are different types of number line. In Kindergarten students might place numbers on a line, but it is often more like a “number row” than a number line … that is, the precise placement is not attended to. In Grade 2 Common Core, the number line is really meant to have a measurement aspect to it. You have a 0 and 1, then you mark of the line in lengths equal to the length from 0 to 1 in order to get 2, 3, etc. At least, you start doing that in Grade 2 … and in Grade 3, the measurement aspect becomes salient when you start talking about fractions. I suspect that all the different sources you are looking at are really talking about different incarnations of the number line.

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