Addition and Subtraction should be taught in unison. I often find that if they're taught as separate entities, children have a harder time with subtraction skills. I use the Frayer Model to begin any new concept to see what children already know or what connections they have.
This model can be completed as a whole class or in small groups. You begin by placing the words Addition and Subtraction in the middle. Students then go through the chart. Once the Frayer Model has been completed, it is hung somewhere in the room to periodically review or to add more things to as your lessons move along.
I do encourage the teaching of both concepts simultaneously. One of my favourite resources to begin with is dot plates. Below is an example of a simple math talk activity to give you an idea of how I introduce addition and subtraction,without using those words.
First, ask the students what they see. Listen for their responses. You may hear things like "I see four and four" or "I see eight." Ask how they know. Use language such as "how many", "more", "less", "how many more makes...", "altogether...." Pose possible scenarios such as "If I moved four dots over to the first frame, what do you notice?" or "If I took four dots away from four frames, what do you notice?" Eventually, students will use words such as "add" and "subtract" or you may introduce them slowly. Using number to talk about helps encourage the use of productive ways to share strategies and ideas about addition and subtraction concepts.
Revisit the Frayer model a few times between your math chats to see if students can add more things to the chart or to notice any misconceptions they may have had.
Second, play math games! Children love them and I encourage playing them every Friday. We have fun math Friday day. One of my preferred games is "Either Way Wins". I developed this simultaneous addition and subtraction game with a horizontal or vertical number line. Students begin at the number 10 and learn to move along the number line by selecting a zero, one or two addition or subtraction card. The student who gets to zero or twenty first is declared the winner. This is part of a four pack of addition and subtraction games that includes Sum Power, Let's Play Add-It, Let's Play Minus, and Either Way Wins.
Finally, I highly recommend your look at borrowing or purchasing Sharry Parrish's resource called
Number Talks. It really has helped anchor my students' understanding of addition and subtraction facts. Pencil and paper tasks will never allow you to see what children fully understand. This is an excellent way to watch the interaction of mathematical thinking. Visit the following website for more information about this:
http://www.mathperspectives.com/num_talks.html
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