The pumpkin life cycle can become a great science lesson for young children. You can discuss plant growth and reproduction as well as teach about decomposition and composting when it comes to disposing of jack-o'-lanterns after Halloween. Try getting a series of pumpkins in various states of growth and have students observe the differences in size and color between small pumpkins and full-size, ready-to-carve orange pumpkins.
Because of their round shape, pumpkins are a great tool for teaching mathematical concepts like circumference, or even volume once it has been scooped out, to older elementary children. Teach estimation by having students guess how many pieces of candy or other countable objects the carved-out pumpkin can hold. Award a prize, like some or all of the candy, to the student with the closest estimation. Carving and decorating pumpkins can also be a great lesson in geometry as students choose shapes to represent different facial features.
Younger children should not be allowed to use carving tools without proper supervision and assistance, but they can still decorate smaller pumpkins with markers and other craft supplies. Miniature pumpkins make for a fun art project and can be purchased at most grocery stores in the weeks before Halloween for fairly cheap: give one small pumpkin to each student and let him decorate it however he wants. When the crafts are completed, students can take them home to display on Halloween.
Since Halloween is a time of costumes, use orange construction paper or paper plates and markers to let children design their own jack-o'-lantern masks. You can also have them make a simple papier-mâché jack-o'-lantern, using a balloon covered in newspaper pasted on with a flour-and-water mixture, which will act as glue. Once the flour-glue mixture is dry, students can paint their jack-o'-lanterns.
Roasted and salted pumpkin seeds are a delicious and nutrient-rich snack. If you carve a jack-o'-lantern with your class, save the seeds and roast them for a fun Halloween snack. Simply rinse off and dry the seeds and spread them evenly on a cookie tray. Coat them with vegetable oil or melted butter and sprinkle with salt. Bake them at 275 degrees Fahrenheit for 10 to 20 minutes, or until they are golden brown. Divide them among students and enjoy.