Help your son find the relevance and discover the interesting side of what he is studying. If the topic is land forms, take him to a science museum so he can see rocks, fossils, and models of volcanoes. If the class is studying the United States government, help your son find appropriate websites or intriguing books on the topic.
Find out if there is a teacher supply store near you and look for high-interest materials on the topics your son is studying. You may find that he will be more interested if he is encouraged to go further with the topic than has been assigned. For example, if the class is studying the U.S. presidents, your son may enjoy building a model of the White House and learning some of its history.