Reflecting on student teaching evaluations

I recently received my student evaluations for teaching last semester. I was pleased to see that the scores were very high and students made many positive comments about my teaching and the course.
I would like to think this is due to my brilliant performance. But it is not.
This years positive results are in contrast to several years ago when students in the same course were so unhappy that they met with the head of department to complain about me and the course. That year many students failed. This year more than half the class got the highest grade possible.

What brought about this dramatic change?
What did I do?
Actually, virtually nothing! The course content and difficulty is the same. The assignments and exams are basically identical, as they have been for the past decade. I did minor fine tuning to my lectures, as I always do, and to the assessment mix. Students also do a pre-test to check prior knowledge and the tutorials are more student led.

The real significant change is the students. From year to year a small class of 5-15 is prone to significant statistical fluctuations in student quality and attitude.
Furthermore, I believe that the ethos and atmosphere in such a small class can be significantly shaped by a few individuals with strong personalities.
Positive attitudes such as hard work, interest, politeness, curiosity, enthusiasm, humility, punctuality, diligence, ..... affect others.
Similarly, negative attitudes such as laziness, boredom, rudeness, arrogance, lateness, whining, a sense of entitlement, ...  can sour a class.

I think the main difference in the student evaluations and their results reflect not my performance or the quality or difficulty of the class but the composition of the class.
I post this because this dependence on student quality seems to be rarely considered when the teaching of faculty is evaluated, particularly by administrators.

Teaching and learning is a two way street.