As with any monopoly, the incentives for public school administrators are all out of wack. Adding a CS curricula takes real time and effort (lost summer vacation time, effort required to convince the board/PTA, picking a curriculum, hiring teachers for an unfamiliar topic). It brings with it real risks and headaches (budget issues, vulnerability/ignorance in a new domain, possible failure/embarrassment, board/PTA conflict, dissatisfied students/parents). Meanwhile the benefits are not tangible and the cost of not implementing a new CS curriculum is zero.

For public school administrators (as with all process owners) it's far easier to simply repeat what they did last year.

On what basis do you say this? What exactly do you mean?

I don't mind that the above claim is cynical. But I think it is (a) wildly overconfident and (b) poorly reasoned. Check your biases. Also check your pain points -- would I be crazy to guess that you've become jaded about student's ability to learn, think, and/or care about education?

Next, consider a specific scenario so we're not talking past each other. Let's say 5% of high schools decide to teach Thinking in Systems. Say they get a grant so that someone experienced (in the book and subject matter) comes in and teaches for a few weeks as a special topic (at no cost to the school).

Now, think statistically and empirically. What kinds of effects will there be on students? If you are intellectually honest, you'll have to ask questions, maybe even gather some data. If you put some effort into thinking, you probably won't conclude there will be zero effect.