One way to teach basic subtraction is to use teddy bears. You can tell a story about teddy bears sitting on a shelf, and how each time a child takes one, there is one less teddy bear. Have the students bring in their own teddy bears, line them up on a shelf, and then count them. Each time a student takes his teddy bear back, count the bears again and explain that the students are subtracting a bear each time. For advanced kindergartners and first-graders, this activity can be done using a worksheet with simple pictures. This allows students to use the subtraction sign and write actual numbers.
Teach students about a few different kinds of bears -- for example, grizzly bears, black bears and brown bears. Tell the students to draw pictures of a forest full of these various bears. Let each student decide how many bears she draws. Tell the students to count how many of each kind of bear they have in their forest. Announce that they are to cross out one black bear, two brown bears, one grizzly bear, etc. Explain to the students they have subtracted those bears from the forest. Tell the children to count how many bears remain.
Talk to the students about what kinds of food bears gather, when they gather it and where they bring it. Using a big teddy bear and make-believe food, have the students help the bear gather its food. When all the food is gathered, ask the students to come up with different animals or other factors (weather, humans, etc.) that might take the food away from the bear. Each time the students remove an item of food, explain they are subtracting something. Have them count how many items the bear has left. A worksheet with pictures and numbers can be used for older students.
Teach older students about hibernation, and how many days a bear hibernates. Students can subtract the hibernation days from the total days in a year to find out how many days the bears are awake. The students also can look at the population of animals in an imaginary forest. Have them come up with a list of how many bears and other animals live in this forest. Tell the students to subtract the number of bears and other hibernating animals from the total animal population to find out how many critters should be left stirring in the winter.