Don’t switch back and forth between all addition facts and all subtraction facts
Teachers often ask me if they can start Rocket Math and do both addition and subtraction at the same time–to help their students catch up quicker. No, don’t do it! It will cause special kinds of confusion (called proactive and retroactive inhibition) as students try to memorize the relationships among the numbers.
Students learning only addition for example, are learning one number family 5*3=8 and 3*5=8. So 5 and 3, no matter which order you put them, they go with 8. That’s pretty easy, no way to get confused. But if students are learning subtraction facts at the same time they have a lot more to remember. On top of learning which numbers go together students have to learn which operation is going on. They also have to remember that 5*3 is sometimes 8, and sometimes 5*3 is 2. And 8*3 is sometimes 11 and sometimes 5 depending on which operation is going on. Switching back and forth from addition to subtraction adds a layer of confusion. It does not make it impossible, it just makes it harder because it is a little more confusing. If you teach only one operation at a time students will find it much easier and they will learn faster and be more successful. That is what we want after all, right?
Can you teach through Fact Families?
Yes, you can. If students learn facts in families (3+2=5, 2+3=5, 5-2=3, 5-3=2) they learn the three numbers as a family. They know if they know any two of the numbers of that family, then they can recall the third number. This is a good way to learn facts. Many teachers prefer it, so we offer it as an option in Rocket Math. The only research I have seen on this showed that learning operations separately, first all addition, then all subtraction, was a bit more efficient than learning through fact families. But there may be a benefit from learning in fact families that makes the fact that it is slower worthwhile. That’s an open question. Would make a great master’s study–especially since Rocket Math has both fact families and single operations available. We have it in the Worksheet Program and the Online Game, so it would be easy to compare and students could be randomly assigned to the condition.