Sorry for any confusion.
Originally Posted by Quantum2003
... the teacher was not trying to palm off her teacher responsibilities... She wants the students to let her know if they are floundering so that she can help them.
seems different than "A letter from the teacher... urging the parents to work with their kids on the reading selection... she would have to make changes if the text continues to be way too difficult."

Originally Posted by Quantum2003
... interpret her letter as... reassurance that the curriculum can be adjusted.
seems different than "it would be a big let-down for DS if the curriculum gets watered down", which some may say indicates a parent sounding concerned, not reassured, regarding changes the teacher's letter states she would have to make if the text continues to be way too difficult.

There seems to be a strong reaction to "threat of lowered curriculum", meaning indication of impending danger of something occurring, much like reading dark clouds in the sky as a threat of bad weather. This definition and use is different than saying the teacher was "threatening" or making "a threat", meaning expressing an intent to retaliate or injure. Same word, two different concepts, distinguished by context. Again, sorry for any confusion. I agree with what you are saying, I share your concerns. Thinking long term, I potentially see greater concerns.