The natural order of things
Not all students are created equal or should be treated as equal
In the best interests of the students who are capable, interested and who want to learn, some kids have to be left behind. That's why our school has streams.
My students don't even try!
The power of expectations
During my training as a teacher, we were told never to call a student stupid. Or lazy. Or bad. Or any other such pejorative. It seems like a sensible prescription, right? Criticize the behavior, not the person.