"The vast majority of states have long granted public school teachers tenure. The way it works is simple: After a certain number of years, teachers qualify—'virtually automatically' in most states, according to the National Council on Teacher Quality—for a form of job protection that makes it extremely difficult to fire them for the rest of their careers.
"The system is analogous to the protections that university professors receive—but with one important conceptual difference. Universities are not just educational institutions; they are our country’s idea factories. And so it makes a certain amount of sense that we would want university professors—the people our society relies on to explore ideas, including unpopular ones—to enjoy protections from ideological or intellectual retribution.
"But this rationale doesn’t apply at the K–12 level. So what is the case for K–12 teacher tenure? The truth is, there isn’t a good one."