Four critical areas of instruction in First Grade are:

1. Developing understanding of addition, subtraction, and strategies for addition and subtraction within 20

2. Developing understanding of whole-number relationships and place value, including grouping in tens and ones

3. Developing understanding of linear measurement and measuring lengths as iterating length units

4. Reasoning about attributes of and composing and decomposing geometric shapes

First Grade students also work toward fluency in addition and subtraction with whole numbers within 10.

(California Mathematics Framework, 2013, p. 85)