Read "Popcorn Plants" by Kathleen V. Kudlinski, or a similar book, to your children, so they can start to understand where corn comes from and the basics of plant growth.
Give each child three clear jars with lids or three sealable bags with zippers. Tell them they are going to plant corn. Ask them to soak several pieces of paper towel with water, to place the towels in their first jar, then to place three popcorn kernels on top of the paper towels. They should seal the jar and label it with a piece of masking tape that says "sun, water" and their name. Tell them to place this jar on a sunny windowsill (If you are using plastic bags they can tape it on or near the window). The second jar should include wet toilet paper, but be placed in the dark, while the third jar should have dry paper towels, but be placed in the sunlight. They should label these jars "no sun, water" and "sun, no water" respectively, along with their names.
Ask the children to write down a hypothesis as to which popcorn kernel will start to sprout first and which one will grow the highest. Also ask them to write down a prediction as to whether the roots or stems will sprout first.
Tell the students to observe and measure their plant growth each day and to record it in a table with the appropriate dates. If you notice that there is no condensation on the bags or jars that received water, add more water to the paper.
Transplant the seeds to pots with soil as they begin to grow stems. The children can continue to monitor the plants for as long as you see fit.
Ask the children to summarize and chart their observations; they may need assistance with this. They should also write a concluding sentence indicating whether their hypothesis was correct.
Organize a group activity where the children create a poster of a corn plant with its leaves, roots and tassel, plus a corn husk where a corn kernel (seed) is highlighted.