Kindergarten · Measurement & Data
K.MD.B.3: Classify objects into categories
K.MD.B.3 is a kindergarten Common Core math standard in Measurement & Data. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
The standard
Classify objects into given categories; count the numbers of objects in each category and sort the categories by count.
In plain words
Classify objects into categories.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
Look at the chart. How many dogs are there?
- 5
- 8
- 3
Where students can get stuck
- Ordering the groups by the space they take up, so 5 large blocks seem like more than 8 small ones.
- Putting the groups in order from fewest to most when asked for most to fewest.
- Sorting by their own rule, such as grouping toy animals by size when asked to sort by whether they fly.
Effective teaching strategies
- Give students a set of large stuffed animals and a rule such as “can fly” or “cannot fly,” and have them sort onto two labeled paper mats, checking each animal against the rule.
- Ask students to count each group and write the number on its mat, so they compare counts and not how much space each group takes.
- Have students put the groups in order from most to fewest, then flip the order to fewest to most, pointing to the written counts to explain.
Units that teach this standard
Find where K.MD.B.3 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Eureka Math
Everyday Mathematics
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Zearn Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Sorting things into groups and counting them for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice measurement and data at home
In Bobby's Math Club, students practice at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free for every family.
See how it works for teachers
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.