Having taught for quite a few years, I must attest that teachers often are cheats. Very rarely do you see teachers actually do what they preach. In fact quite many times a teacher couldn't pass their own examination with flying colors (this is especially true in higher education). Many times the teacher can not even solve their own homework problems, instead they copy the ready made solution from a different source. While this sounds bad, its actually a boon because this way you get less mistakes falling through.
Secondly, teachers tell white lies all the time. Sometimes a very definitive explanation holds much more water than a very well worded "maybe". The thing is not much of our knowledge is as definitive as we might want to think. Often the truth is so complicated that in order for to begin to explain a subject:
- One needs to get a simplified run through.
- Once you attain a specific level, we can tear down the previous knowledge and replace it with a new one.
- and repeat the process.
All explanations are thus some kind of lies. For this to work we need specially adaptive minds. Lots of half mastered people walk out of the classrooms all the time. So maybe most destructive of all, we let people keep their misconceptions as to not show that they were lied to from the beginning. And this is one of the big lies.
Third, there is also some globally accepted self perpetuating lie. Where people assume that having attended A. taught by B. and graded by C. is somehow accurate. Grading is terribly inaccurate, and not at all objective. So be careful when categorizing people by their education or scores. Errors happen a lot, much more than generally accepted. Many societies would in fact collapse with more scrutiny on this matter.
In defense for all good teachers out there. There is little choice, all communication is corrupted in transit and affected by previous misunderstandings. So there's no way to reach the goal. But one thing is certain: no pain, no gain. If it felt easy you didn't learn a thing.