When Gary West taught elementary school social studies two decades ago in a suburb of San Antonio, he wasn’t afraid to take his lessons beyond the bounds of the textbook. West wasn’t told to steer clear of potentially controversial topics, so he shaped lessons that he thought would pique students’ interest. Teaching history, he led discussions about how the founding fathers’ backgrounds—white, wealthy, landowning—might have influenced the way they wrote laws. To teach about the government, he...