I read the question https://math.stackexchange.com/questions/1593091/how-to-explain-why-study-prime-numbers-to-5th-graders and according to the body of the question, some students sigh. Also according to https://psychology.stackexchange.com/questions/20867/why-cant-we-learn-what-we-dont-like, it's sometimes hard for people to learn stuff that's not interesting for them. I don't know which education system the person who asked about teaching prime numbers was talking about, so I decided I don't care to determine which one it is and will just ask about the education system in United States because the fact that some education system has that problem is a good sign that the American one might have that problem as well whether or not it's the same education system.
I think some schools just expect students to figure out what the teacher means by what they're saying and some students just cannot figure out what the teacher means and really struggle with their attempt to. I would love to get an answer by a teacher who is trying to teach prime numbers to elementary school students about what's happening with their attempt to teach them prime numbers. I would like them to tell me what teaching style they're using. I would also like to know what they're having trouble teaching the students in a way that they can understand. Are they trying to get the students to come up with an explanation all on their own of what the fundamental theorem of arithmetic is to teach them how to think for themselves?