CCSS.Math.Content.K.MD.B
The standard
Classify objects and count the number of objects in each category.
Common Core State Standards for Mathematics
What this standard means
Students need to sort objects into clear groups based on one shared attribute, such as color, shape, size, or type. Then they count how many objects are in each group and say which group has more, fewer, or the same number.
Mastery looks like a child explaining the sorting rule, placing each object in only one group, and counting each group accurately. Students often get stuck when an object could fit more than one rule, when they change the rule halfway through, or when they double count while counting a group.
Ways to teach it
- Give pairs a tray of buttons and ask them to sort by color, then count and label each group with number cards.
- Ask, “How did you choose your groups?” and have students explain their sorting rule to a partner.
- Show six mixed pattern blocks, ask students to sort them one way, then point and count each group aloud.
- Use a snack mix, have students sort pieces by type, count each pile, and tell which snack piece shows up most.
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Related standards
- CCSS.Math.Content.K.CC.B
Count to tell the number of objects.
- CCSS.Math.Content.5.G.B
Classify two-dimensional figures into categories based on their properties.
- CCSS.Math.Content.K.CC.C.6
Identify whether the number of objects in one group is greater than, less than, or equal to the number of objects in another group, e.g., by using matching and ...
- CCSS.Math.Content.K.MD.B.3
Classify objects into given categories; count the numbers of objects in each category and sort the categories by count.