Children are most likely to come across negative numbers when using a calculator and they are usually taught about them in the context of measuring temperature. Number lines are also very helpful as they show that numbers continue after zero when counting down.
Here we have a maths worksheet which asks for a series of five numbers, both positive and negative, to be put in order, with the least first. Calculating with negative numbers comes a little later and can cause a great deal of confusion, even in High School!