This would be very easy for kids to participate in. Just buy white carnations and add food coloring to the water in the tubes and watch the flowers change color. this would be very easy for high school and middle school kids.
Soil Erosion Experiment This might look like such a simple experiment but it will definitely show the importance of having vegetation covering the soil to your kids! They will love this hands on exper (Garden Step Long)
I love easy experiments that make science cool! This rainbow colored celery science experiment is simple to set up and really makes transpiration come alive for kids. // Experiment by Coffee Cups and Crayons