Most teachers have heard it in the last year or two. It is apparently hardwired into all administrative training about new evaluation methods.
You will not live in Excellent (or above average or super-duper proficient or whatever language your state prefers). You will only visit. You will live in Mostly Pretty Okay (or whatever).
Imagine if we started out the year by telling our students, "You'll only get a couple of A's this year. You are never going to excel. You will only be mostly pretty okay the majority of the time." And you'll have to imagine it, because who would actually say that?! Not any Mostly Pretty Okay teacher, because we know that expectations matter. I tell my students every year that we are shooting for awesome. I tell them a gajillion times they can do this and they will be great. Because expectations matter.
Even Arne Duncan believes in expectations, to the point of imagining that great expectations can cure students of any disabilities they might have.
But for some bizarre reason, the US has adopted an approach to teacher evaluation that starts with the premise that the teaching staff will be usually Mostly Pretty Okay and rarely Great. How does that expectation lead us to excellence?
Districts that are operating with some sort of merit pay system only make matters worse. They can't afford-- literally cannot financially afford-- to have a staff of uniformly excellent teachers because they don't have the money to pay them all big-time quality pay. So those districts have an actual financial incentive to make sure that their teaching staff is Mostly Pretty Okay.
And so we flounder on in upside-down education world, where we talk about the need to foster and promote excellence in teaching while we structure the system to avoid and smother excellence. It's a reverse emperor's new clothes-- teachers appear clothed in excellence and the emperor insists that they are naked. The good news for students is that teachers will continue to produce excellence whether anybody in power claims they can see it or not.