There is always a range of interpretation. But no one would interpret Socrates (Plato) as denying that knowledge both a necessary and sufficient condition of virtue.
I never said this would be a good interpretation...I agree with your post where you said that for Socrates, "knowledge is virtue", and am not trying to dispute anything you have said about Socrates/Plato, other than the reference to learning what we were taught in school, because on this matter, people are taught very different things.
I'm only trying to point out that, there are a wide range of interpretations, some of which differ quite significantly, and it is important to not just take one of them as being "correct"; at some point you have to make up your own mind. You have to keep an open mind when reading Plato's works, and when reading others' interpretations. Sometimes it is clear, other times not so much.
As an example, there are many professors throughout academia who still do not agree on The Republic
. Some of high repute will insist that it was Plato's sole intent to construct an actual city in this work. Others of high repute, like Strauss and Bloom thought that this work was really more of a thought experiment for students, and the goal was not to construct a real city. And yet there are many professors who will also teach that the entire thing was written as an analogy for how to best govern the soul (this is how it was in my case).
Some people might say that Plato's intent was not important, but of course there's a huge difference in interpretation depending on what you think the intent was. There is good evidence to support all of these interpretations of the republic...so which one is right?
Certainly, when in the course of the dialogue we learn at least what are the wrong answers.
Indeed we do...and this is definitely progress.