The arguments about whether school administrators who haven't been classroom teachers can effectively evaluate teachers is never-ending. At the heart of that argument is actually whether teaching is a professional skill requiring great expertise, or whether, as some business-minded people seem to think, it's a skill that anyone can do, with as little training as possible. But can an administrator who has never faced the day-to-day management of a classroom full of students adequately pass judgment on the quality of a teacher? I would say probably not. Before the barrage of emails start, let me clarify my reasoning for using the word "probably."
To teachers who think I should have used the words "definitely not" instead of "probably not," let me say that I don't think there are absolutes here. There are certainly administrators out there who have enough intuitive understanding of what "good teaching" looks like that they might be able to do an adequate job of evaluating teachers. But, and this is important, I think that is by far the exception.
In the United States, there is a prevalent belief that somehow a successful businessman is capable of "super-heroic" feats and should be respected as capable of doing anything---from being a great leader to a politician. This is evident in how many times political advertisements display proudly the title "Successful Businessman" as if that somehow automatically qualifies them for office. As an offshoot of this belief is the idea that a person who's managed a thousand-plus employee corporation can somehow step into a school and manage it just as well. The same thinking seems to apply to those who are military leaders. They also are somehow revered by some and seen as fully capable of managing schools and districts simply due to their established leadership abilities, and this includes the evaluation of educators. But I submit to you that neither business leaders nor military leaders are always capable of managing educational organizations. They are definitely not always capable of judging the effectiveness of classroom teachers simply because when they do judge teaching, they automatically see teaching as a simple task of "imparting knowledge" to students and not a complex set of experiences and activity that are designed to make the deeper learning of critical thinking, problem-solving, creativity, etc. possible. Sure, these business leaders quite often are creative and experienced people when it comes to solving problems. But their experiences lie within organizations where employees are easily dispensed with, and if products are defective, they can be simply discarded. In the educational enterprise, we can't dispense with students when they are somehow not measuring up like so man defective parts; we have to teach them from where they are. Also, while we could easily fire teachers not quite measuring up, we then have to face the issue of trying to find another teacher in a climate of fewer teachers and fewer young people becoming teachers. In fact, most teachers, and I would add principals, don't fall into the black and white categories of "good" and "bad." Most fall in the middle where evaluation is incapable to making those extreme categorizations. Instead, good administrators are often in positions of working with all teachers to move and improve to the "good" category.
Classrooms are very complex places. After having spent 16 years of my 25 years in them, every single time I enter one to evaluate a teacher, I always remember that. It does not translate into a sympathetic lack of will to honestly complete the evaluation; it simply means I view classroom teaching through a lens of complexity that allows me to see many more of the subtle things that happen as a teacher engages students. It took time for me to develop that lens. I think it fair to say, that lens allows me to better understand teaching and learning, and it makes me a better evaluator.
Often, when an administrator has never been in the classroom lacks having this lens, he must resort to the only lens he has, which is often tinted with a superficial understanding of teaching and learning. That means he grasps for simple evidences of good teaching like test scores, attendance, and graduation rates, which are numerical in nature and easily placed on a yardstick. He doesn't see teaching through a lens of complexity and understanding. It is for that reason, I would say that administrators who have taught for a period of time themselves understand "good teaching" better. Those at the extremes of good teacher and bad teacher are certainly easier to recognize, so the non-teaching administrator could easily recognize their expertise or lack of skill. It's all those in the middle that need the coaching and support that escape the black and white categorization of a superficial understanding of teaching and learning. A non-teaching administrator is often simply incapable of seeing the complexity of teaching.