This is the standards chapter in the Principles and Standards for School Mathematics of the National Council of Teachers of Mathematics. Select Measurement from the left column for across-the-grades standards. For specific grade level standards select Pre-K - 2, 3 - 5, or 6 - 8, from the top row. (
http://standards.nctm.org/document/chapter3/index.htm
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An interactive lesson for visualizing, estimating and measuring, from the electronic examples of the Principles and Standards for School Mathematics. (Pre-K-2) (
http://standards.nctm.org/document/eexamples/chap4/4.3/index.htm
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An interactive lesson of estimation activities from the electronic examples of the Principles and Standards for School Mathematics. (Pre-K-2) (
http://standards.nctm.org/document/eexamples/chap4/4.6/index.htm
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