## Reflection: Vertical Alignment Numbers 20 to 25 - Section 3: Practice

Leaving Kindergarten, students need to have a flexible understanding of "number". For example, that ten can be created by five plus five more, as well as by six and four more. Also, that ten can be made by taking some away.

They need to be growing their mathematical communication skills, with an understanding that their thinking is as critical as "the answer". Kinders should be accustomed to working alongside peers, and comfortable with explaining their thinking to others using words, pictures, fingers, and other representations.

When leaving kindergarten, students should have had extensive practice with subitizing  -- the instant recognition of relatively small quantities. This is an important step in the development of number sense, and the skills of addition and subtraction.

Mathematics Learning in Early Childhood (National Research Council 2009), has broken down the Common Addition and Subtraction Situations, to show the progression of mathematical thinking.

This is a very helpful document for kindergarten, first, and second grade teachers because it allows us to align our curriculum vertically, and to make sure we have no gaps in the growth of these different situation of addition and subtraction.

Critical K Understandings
Vertical Alignment: Critical K Understandings

# Numbers 20 to 25

Unit 9: Numbers to 100
Lesson 2 of 8

## Big Idea: Numbers don't stop at 20! We spend the last week or so of school looking at the numbers beyond 20. Today we do it through a story.

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Standards:
Subject(s):
Math, Number Sense and Operations, Numbers and Operations, Numbers, Math and Literature
60 minutes

### Christina Yingling-Smith

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