The official justification for tenure is that it allows scholars to “speak truth to power” without fear of losing their jobs. There’s obviously something to that, but I’ve always looked upon tenure as a form of non-salary compensation. Most college professors make less than they would in other sectors. Tenure compensates us with much greater job security.
I’d never thought about it in these terms, but the same reasoning might also apply to teachers in primary and secondar education. It turns out that while direct evidence for schoolteachers proves difficult to come by, data on New Jersey superintendent pay suggest some truth to the tenure-as-substitute-for-pay hypothesis.