The cups in the egg cartons are about the right size, and the larvae seem to find them satisfactory. About three weeks later, silk moths will emerge from the cocoons. They do not fly or eat. They look for mates, lay eggs, and die in just a couple of days. The eggs may be collected, and refrigerated until the following spring when the project can be repeated.
Some teachers like to harvest the silk.
In this case, the cocoons are cooked to kill the pupae. Then, they are unraveled by placing them in warm water to dissolve the natural adhesive that is present. With young children, simply observing and recording growth and development may be enough. Experiment and find out. Drawing and writing about what they observe are always good ways for students to record their observations.