Here is one recipe. You can vary the proportions to make the candy stiffer. I would use either more peanut butter or less syrup. You can also roll the pieces in powdered sugar to make them less sticky. I think the ones at school were made into long rolls, flattened a bit, and then sliced into individual small servings.

1 cup peanut butter 1 cup powdered sugar 1 cup light corn syrup or honey 1 1/2–1 3/4 cups powdered milk

Instructions: In a large bowl, mix the peanut butter and corn syrup (or honey) until well combined. Gradually add the powdered milk and powdered sugar. The mixture will become very stiff. For the best result, switch from a spoon to kneading with your hands to fully incorporate the dry ingredients. Press the mixture into a greased or parchment-lined 8x8-inch pan. Refrigerate for at least 30 minutes, or until firm. Cut into squares or rolls and serve.