So far this year I have noticed several students making the same errors when subtracting. For example, with 5 – 3 student kept saying 5 was the answer. And for 2 – 2 they answered 2. So, I watched what they were doing. They were using their fingers as if the problem were an addition problem and then they subtracted the subtrahend. For 5 – 3 the students put up 5 fingers, then 3 more fingers, and then they subtracted the 3. When they are doing this, they think they are doing it correctly. To me this means they have a procedural understanding of addition. They are overgeneralizing that procedure with subtraction.

Additionally, this was observed with more students earlier in the year and is now only observed with students who have not transitioned to a better understanding of addition and subtraction. So, this makes me wonder if all students go through this or if it is just my tier 2 and 3 students.

Another common error I keep seeing is when subtracting 0 students answer 0. It is unclear what they are thinking on this right now. I will be asking them how they know that in the near future. We have mostly worked on addition and counting/number recognition than with subtraction.