Why do teachers say they work for the school board?

I'm perplexed by how many teachers I find who talk about working for the school board. It seems like a weird thing to me.

Realistically, teachers report to their principal. The principals work for the superintendent. The superintendent is selected by the board.

In business, most people when asked who they work for, will either cite their boss or the president/CEO of the company. I've never heard of anyone is business talk about the board of directors as who they work for.

In non profit universities and hospitals, I imagine people work for the dean or president or executive director.

What is it in some parts of the country or some school districts that this language of working for the school board has taken hold?  I'm suspicious that it's a load of C***.  Specifically, I think it's almost Orwellian in that it highlights the role of a board of frankly amateurs and denigrates the role of the professional superintendent.

Any thoughts anybody? Any insight?