Under a colorful schoolroom ceiling, with a hand-painted periodic table of elements radiating rainbow overhead, close to three dozen high school students hover in groups around laboratory stations. Mr. Johnson’s chemistry class at Sylvan Hills High School in Sherwood, Ark., normally isn’t this crowded. Today, Ms. Brannen’s art students have joined the science students for a lesson on how art and chemistry collide. “Art interacts with all subject matter,” Brannen says. “For me