Study your yard to find a place that gets full sun at least 6 hours a day. Choose a spot up against a fence.
Dig a hole 6 inches deep for each beanstalk you plan to grow. Place the hole about 6 inches away from the fence. Make each hole about 6 inches across.
Shovel in one trowel of compost. Fill the hole back up with soil until it's within 1 inch of its original height. Have your child place two bean seeds on top of the dirt in the hole.
Demonstrate to your child how to cover the bean seeds with the remaining inch of dirt, patting down the soil with the back of the trowel. Continue digging and planting holes all along the fence until you have the desired size of bean crop planted.
Water the seeds thoroughly and keep them watered throughout the season. Beans need about 1 inch of water per week to grow well, so supplement rain showers with water from a hose or sprinkler.
Watch the beans grow until they have two sets of true leaves. Choose the stronger of each pair to keep and pinch off the weaker one at the surface. This will ensure that the nutrients go to the plant with the best chance of making lots of beans.
Pick beans from your beanstalks when they are solidly filled but before they get lumpy with large seeds inside.