When I was an elementary school student, schools in my hometown administered IQ tests every couple of years. I felt very scared of the psychologist who came in to give those tests.
I also performed terribly. As a result, at one point, I was moved to a lower-grade classroom so I could take a test more suitable to my IQ level.
Consequently, I believed that my teachers considered me stupid. I, of course, thought I was stupid. In addition, I also thought my teachers expected low-quality work from a child of such low IQ. So, I gave them what they expected.