Some teachers are good, and others lack common sense. I hope this post serves as a guide for giving bad examples to make sure students don't understand anything.
These are some of the bad examples I encountered as a student.
Teacher: This is how we solve exponents. (After some theory.. blah blah).. So to solve 22 we multiply two with itself twice which is 2*2 = 4. Does everyone understand how exponents work?
Students: Yeah. We get it. 22 = 2 x 2 = 4
Teacher: OK so what is 34
Students: Well that's easy. 34 = 3 x 4 = 12
Teacher: Oh no. you don't understand??
Whose mistake is it?
Case in point: Even if you give a complete theory, you can easily ruin it with a bad example.
Do you have any other examples of bad teaching that you want me to update here? Mention in comments.