English teachers are deciding which books to skip. History teachers are condensing units. Science teachers are often doing without experiments entirely. With instruction time reduced as much as half by the coronavirus pandemic, many of the nation's middle school and high school teachers have given up on covering all the material normally included in their classes and instead are cutting lessons. Certain topics must be taught because they will appear on exit exams or Advanced Placement tests. But teachers are largely on their own to make difficult choices — what to prioritize and what to sacrifice to the pandemic. “I have to make decisions constantly about what material I’m not going to cover because it is impossible to get it all done,” said Leigh Foy, a chemistry and Advanced Placement biology teacher at York Suburban High School in Pennsylvania.