Mike has given us some pretty good reasons why schools need to provide a solid education in core disciplines and fret less about so-called "21st Century Skills." I'd add to his list that schools need to focus on core subjects to offset the underexposure to them that too many kids get at home.
Witness Franklin County, Ohio, home to the capital city of Columbus: Franklin County's unemployment rate is 5.8 percent (compared to a statewide rate of 7 percent) and its median household income is $45,459-besting the state average by 5 percent. It is the seat of state government, home to the largest university in the country, and boasts the state's top-performing urban school district. Yet Franklin County's adult illiteracy rate is a whopping 13 percent (up from 8 percent in 1992). Many of these non-readers immigrated to the United States as adults, so this isn't to say that our education system failed them. But the children of illiterate parents depend greatly on our schools to teach them the basics like reading, writing, and arithmetic, and to expose them to history, literature, and the arts.