Oh boy, middle school students evaluating a lesson is like a Mongolian evaluating a movie in Spanish. If the students are not entertained, you are a bad teacher. Trust me, I've been there and done that in China. To be fair, I do try to do edutainment and I struck out as much as I succeed when I do my lesson plans for the week. At one point I was so frustrated with my middle school students that I showed a movie for three weeks before I figured out something to get their attention back.
Added to that, I have done things at my middle school that I never dreamed of before. I've walked out of class because of the level of disrespect; I got in the face of a kid who was a spoiled little brat, and I even.... well never mind the last one but after that the kid never did that again.
SB, I do not have in mind young children evaluating their teachers but older ones such as those in high schools. I have known of a high school that required students to evaluate the lesson given by a foreign teacher applying to teach English at the school. The students had to fill in some evaluation form.