Whenever a college student asks me, a veteran high-school English educator, about the prospects of becoming a public-school teacher, I never think it’s enough to say that the role is shifting from "content expert" to "curriculum facilitator." Instead, I describe what I think the public-school classroom will look like in 20 years, with a large, fantastic computer screen at the front, streaming one of the nation’s most engaging, informative lessons available on a particular topic.