You are both right. My wife teaches in a school where many of the kids come from single parent households and many are brick stupid. There is a group of teachers in that school who attempt what I call polishing a turd and do their best to work with the dummies. My wife in particular has a reputation for dragging kids over the passing line for standardized tests. Do they succeed in imparting knowledge, results vary, but I would defy someone to do better. OTOH there are many teachers who are just there for the paycheck and do little more than house the kids for 8 hours.
If I saw that two or three in 10 teachers received the highest marks, even in a horrible district, I would believe it. 8 in 10 means they are not properly evaluating.
"It all depends on what the meaning of the word "is," is.."