Actually, this conclusion is incorrect. Trained as a teacher, and having taught, as well as having been a part of an organization providing consultation to a legislative Task Force on Excellence in Education, my suggestion comes from both research and experience, and it has been the opinion of many who have worked to penetrate and change the vast bureaucracies which control and impact on the sad state of K-12 education in the States.
That aside, decades of control by the combination of Liberal/Progressive political and union power on the bureaucracies and schools of the nation have had their consequences--not many of which have made the improvement of the learning performance of children become better.
What organization is that? I stand by my statement that you cannot evaluate teachers based on student performance because I have personally had students who cut class, disrupted class no matter what measures you took, failed to submit work despite being informed what consequences that would bring, failed to study or even show up for tests, etc. My colleagues have all had such classes as well, which are becoming the norm in NYC. The master teacher of the world could not have a successful outcome with such students, particularly when they well know that the teacher HAS to pass them and so they can continue with the above behaviors and still get a passing grade. So how fair is that to the teacher, who has worked hard on their lesson, tries their utmost to teach the lesson while everyone is texting, watching videos, making calls(!), etc. with their cell phones (thanks to commie mayor Dumblassio, who now allows cell phones in the classroom), comes into your classroom with very low reading levels (having been passed along to higher grades which they never should have), can barely write, etc.? It is not.
Even though unions have become very corrupt and absolutely useless leeches on teachers’ salaries, while delivering very little in the way of services, you cannot blame unions on the poor performance of the students. The blame is largely on the lib-prog policies foisted onto the administration of schools by politicians, and the parents of the students who send their kid to school utterly unsocialized to function in a classroom setting. The teachers try their darnedest, but honestly, it’s like hitting your head into a brick wall with these conditions.