What does this paragraph mean?

Basically in order to be a successful teacher one needs to remain calm and not get too emotionally invested in pupil's behaviour/progress, the flip side of this is that an unruly pupil will probably be allowed to fail.

It's over wordy and misleading, whoever wrote it seems to feel a need to show how smart they are. Instead they put a lot of people off, and don't impress anyone.

I agree that it's very badly written.

I like your answer so much, but I still could not understand "have much power over teachers' lives" , could you help me again?

Pupils can't do much to damage teacher's careers, but teachers can make life very difficult for some pupils if they want to.

I cannot agree more. This paragraph cones from a artical of a translation contest. The whole passage is so weird and complicated, making me crazy!

oh, you are so nice! thank you for helping me!

One knows intuitively, when teaching a child, that only the utmost care and patience will ever work: one must never shout, one has to use extraordinary tact, one has to make ten compliments for every one negative remark and one must leave oneself plenty of time…

All this wisdom we reliably forget in love’s classroom, sadly because increasing the level of threat seldom hastens development. We do not grow more reasonable, more accepting of responsibility and more accurate about our weaknesses when our pride has been wounded, our integrity is threatened and our self-esteem has been violated.
some times i find it's difficult to understand foreign
people' passage and their use of word such as "negative remark" and "reliably forget" oh, i am so confused! could you help me?

A negative remark is criticism, like messy handwriting, poor sentence structure, that sort of thing.

Reliably forget is the author's attempt at humour, they're suggesting all teachers will forget what they're taught about classroom management once they start teaching and rely on gut instinct.

All this wisdom we reliably forget in love’s classroom, sadly because increasing the level of threat seldom hastens development.
i appreciate your excellent answer, but how to understand
above sentence? thank you so much!

Kids don't learn more if they feel threatened.