12 vs. 21: Strategies for Kids that Struggle with Reversals

Many young children reverse numbers (like 12 vs. 21) and letters when learning to read and write, which is normal for most Pre-K, Kindergarten, and First Grade kids! It’s just part of the growing process of becoming literate. Unless the child has a true learning disability, most of them outgrow it and can work past it. Meanwhile, what can you do to help?

If you are a parent or teacher looking for information on dyslexia or dysgraphia, you can learn more here.  This post isn’t about dyslexia.

Disclaimer:  Although these activities won’t “cure” any learning disability that includes letter, number, or word reversal, they should help!  But for the kids that occasionally reverse or mix up a couple of numbers or letters, these activities might just turn things around!

In this picture, the children are building stacks of 12 or 21 on top of the SitSpots with the numbers written on them.


Of all the concepts that need to be taught in Kindergarten, the simple task of  recognizing which 12 vs. 21 can be one of the most difficult for many young children! I have always had several Kindergartners who were never able to get the numbers in order to 30 simply because they could not tell the difference between the 12 and the 21.  There are other skills that those children do not pass either, purely due to this confusion, such as matching sets to 30 and place value types of activities and writing the numbers.

Using manipulatives to show what the numbers REALLY mean is ALWAYS a great idea!  In this case, I used pompoms.

Clearly, this is a question of how well-developed their visual perception skills are, how much exposure to print each individual child has had, and whether or not the child consistently progresses from left to right when reading.  So below are some activities that have helped my students in the past!  I hope that they are helpful!

Prompts and Strategies to Help Children That Are Struggling with Reversals:

Here are some prompts and strategies that might help struggling children. Hopefully, the children will start to learn some of these “tricks” to help themselves remember which number is which by the time they have done several of these activities. Try them all and see what helps individual children the most because you never know what will work!

1. Try a musical approach.

Remind them of “The 12 Song” and “The 21 Song” from Number Jumble, or “The 12 vs. 21 Song” from Musical Math Vol. 2 as needed. Singing a song (and doing the movements, too) helps light up a part of the brain that may trigger children to remember a certain song and, therefore, the number that the song is teaching.

2. Teach kids to figure out their left or right side.

Help them figure out which side is their left by teaching them to hold up a hand and make an L. If the L is heading in the correct direction, that’s the left side.  Some children may figure out which hand is their left hand by knowing which one is “their pencil hand” and by knowing if they are “a lefty” or not.  For most of us, the hand we write with is our right hand.  “We write with our right hand.”

3. Ask children to close their eyes and visualize the arrow (from the 12 Vs. 21 Sort Flash Cards) in their minds.

What does it look like? Where is the dot, and where does it begin? Can they put their finger on that imaginary dot and run their finger along that imaginary line?

4.  Match the number to one on a number line.

Have the child count the number line to the number they think they’re looking at, touching the numbers one at a time.  Then, have them place the number on the flash card right underneath it.  Do they match?  Touch them.  Are the two numbers in the same place?

Five Ways to Help Children With Reversals

Here are FIVE different ways to help teach young children with reversals, especially if they are reversing numbers and learning to tell the difference between the number 12 and the number 21!  These activities should work the same for any basic “look-alike” numbers, letters, or words that a reader consistently confuses.  Some classic look-alike letters are b/d, p/q, w/m, n/u.  Some look alike numbers are 6/9, 12/21, 13/31, 14/41, 15/51, 16/61, etc.

1.  Build the Numbers with Blocks and Label Them.

Children must first understand that there is a difference in the quantities of each number. 12 has one group of ten and two 1s, but 21 has two groups of ten and one 1.  (It’s even a little confusing to try to write it down!)  But when children work with blocks to build those two numbers and then practice labeling them, things start to get a little clearer! For kids who reverse words, have them build the words and label them with pictures.

Here is a SitSpot with base ten blocks to represent number 12. SitSpots are made with VERY STRONG Velcro that you can write on with a marker!


2.  Play Games with the Numbers

Number recognition games are always a good thing to help kids with this, but sometimes I think it’s necessary to narrow it down to just the trickiest numbers (or the ones they need) and use THOSE for the game!  That’s how I came up with “The 12 vs. 21 Game!”  For children that reverse letters or words, just play the game with letters or words instead.

The numbers were written on SitSpots.  And the big, soft die with the color words on it was part of a large game set I bought years ago that is no longer available. But I found a similar “dice with clear pockets” on Amazon.

Preparation:  I decided to make this a life-sized path game, so I cleared a spot on the carpet.  I wrote lots of 12s and 21s on those wonderful Sit Spots for my game and laid them down in a figure 8 design, indicating a starting and ending point for the kids.  However, you may want to simply lay down or tape some index cards.  I really had too many of the spots for the game; half that many would have been fine (maybe 25-30?)  The other alternative is to play it on paper rather than on the carpet “live.”

“The 12 Vs. 21 Game” plays just like CandyLand, except that each colored spot has a number 12 or 21.  Children roll a colored die and move their marker up to the nearest color that they rolled.  For example, if the child rolls a blue, he moves his marker to the next blue space.  Then he reads the number on that blue spot.  And THEN, while the others take their turns, he has to build that number using base ten blocks.  The first person to make it to the end is the winner.  Watch the video below to see how we play it!

3. Sing About It!

If you just watched the video above, you probably heard the 12 vs. 21 song from our Musical Math Vol. 2 collection, available on our HeidiSongs.tv Video Streaming site! That is one of the songs I wrote to help children internalize the difference between the two numbers.  We have Sight Words Song collections that are great for little ones who struggle with reversals or other reading issues.  Check them out here!

Our Number Jumble 0-30 collection has a song that teaches kids to write and recognize number 12 and another for number 21! In fact, there is a song for each number, 0-30!


4.  Get Some Flash Cards and Sort Them:  Is It a 12 or a 21?

This is a picture of the 12 vs. 21 sort free download, but using pom poms to show the quantities rather than the ten frame cards.
For this activity, all you need are some flashcards with 12s on them and 21s on them.  You can make your own or download mine here.  (My set also has blank cards included with the arrows and dotted lines, so that you can adapt them for letters and words.)  Mix them up, have the children pick one, and decide which pile it goes into.  Is it a 12 or a 21?  To make sure that the child is not just guessing, have him or her explain how he knows what it is.  For example, he might say, “I know it’s a 12 because the one comes first, starting on the left.”  For children that reverse words such as “was” and “saw,” have them sort the words instead of numbers, following the same procedure.

Here is a suggested lesson plan for sorting 12s and 21’s with children that are struggling with reversals:

1. Practice sorting the 12/21 cards from set one with the arrow below them (12 Vs. 21 Sort Arrow Version). The children should say the number aloud each time they sort, reading it by running their fingers under the number from left to right.

2. Once your kids get pretty good at the “12 Vs. 21 Sort Arrow Version,” switch to the cards with just the dotted line on the bottom, “the 12 Vs. 21 Sort Dotted Line Version.” Remind them to visualize the arrow in their mind. Where would it start from? Keep having them say the number aloud each time they sort, reading it by running their finger under the number from left to right.  (If children are struggling, mix the arrow cards with the dotted line cards.)

3. Eventually, the hope is that you will be able to switch to the plain 21 vs. 21 cards and that the children will be able to identify the numbers without getting mixed up. Keep reminding them to visualize the arrow in their mind. Where would it start from? Encourage them to run their finger under each card from left to right as they read it aloud.

If children are struggling, mix in the cards with the arrows and/or the dotted lines, and then gradually remove those cards with these supports.  When you combine all three formats together, you may get an insight to see if the children are doing better with the dotted line at the bottom, with the arrow at the bottom, with the flashcards with no cue at the bottom, or if those supports make no difference at all.  This may help you figure out what will help confident children in the future if they reverse letters, numbers, or words.

5.  Do a 12 vs. 21 Roll and Graph Race
For this activity, download the graph and the printable dice here, and have the children roll the numbers. Each time they roll a 12, they color in a 12 box. Each time they roll a 21, they color in a 21 box. The first person to fill in any row to the top is the winner. The download also contains blank graphs and dice so that you can adapt this activity to words, letters, etc.

You can use a plain old block as a die and print the 12s and 21s on the block.  That’s the easiest way!  The younger the children are, the more likely they will “squish” a paper die.  Another alternative is to put a foam die inside the printable dice provided so they don’t get squished.

If you are worried about possible signs of dyslexia in your child, check out my blog post, “Signs of Dyslexia?”.  I also suggest going to the Yale Center for Dyslexia and Creativity for expert, up-to-date information and guidance for more in depth information on what dyslexia is.

Click here to view my post on some student work samples with what I consider “normal reversals.”
-Heidi 🙂

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