The reason you can see the flames at the top of the dryer is that the design is counterflow so that the heat is above the fabrics which was determined to be safer than having it below the fabrics. The fan sucks the heat down through the fabrics and out of the dryer.
If your son has not done much laundry, have him practice some before leaving for school. Maybe he will meet someone there who will help him on the finer points. You can find a magnetic-mount thermometer that he can put on the dryer door to give him an idea of the temperature inside the dryer. The heat does not have a tendency to do damage until things are dry so tell him to be careful and not overdry fabrics.