Take different size pumpkins, pies, apples and candies to teach about circles. Paint or carve a pumpkin to create a face; tell the children what shapes you used to do it.
Set out candy corn and triangular-shaped Halloween candies on a table to show what a triangle looks like. Have the children glue candy corn on paper, forming triangular shapes.
Lay out square trick-or-treat bags and have the children fill them with square Halloween candies to learn that squares have four equal sides.
Decorate the classroom with star-shaped objects, then point to them, saying "star." This will help your pupils learn what a star looks like and remember its shape.
Lay out different shaped Halloween candies that are circular, square, triangular, rectangular, and heart shaped. Have the children tell you what each shape is to make sure they are learning. If they get the shapes right, reward them with candy.