Negative numbers are very confusing to a lot of people. I hear a lot of teachers saying, “you can’t do that,” if a student writes 5-7 (instead of the actual question of 7-5). What I would like to hear is something like “Right now we are only subtracting the smaller number from the larger number.” I say this because it’s my pet peeve about math and when we get into negative numbers we can do that. I used to do it regularly with my bank account when I was a starving student. Why set a child’s mind up for future confusion.
I also think that the idea of negative numbers should be introduced in preschool. Especially if you live in a climate where it does get below 0. That would be a perfect real life example to bring to the children. As for me I live in a very temperate climate so I just put up a number line that goes from the floor to the ceiling that includes negative numbers. I also talk about if you borrowed apples from a friend and negative numbers are as if you owed someone apples back.Just introducing the idea that there are such things as negative numbers is helpful. It is like having a preview of what is coming.