I agree this to some extent. I had a teacher who said conduction(thermal) does not happen in liquids and gases. Even according to textbook, fluids does convection and radiation but no mention of conduction, and there was an excersise question:

Conduction occurs in _______.

a) Solids b)Liquids c)Gases d) All of the above

The answer in teacher's manual was (a) and I(and my friend) disagreed on that and argued. The teacher actually belived it happens only in solids and she was against me. I even wrote the "wrong" answer as per teacher on exam and lost 1 mark in that exam. And finally we got redirected to a senior teacher who said I was correct but the manual for teachers said so because they thought that shoul be introduced in higher classes only. It was pretty unacceptable to me as they don't NEED to say the wrong answer and they can simply say conduction occurs in fluids as well. It bought more problem than what it would have been if real answer was given. Even the teacher belived fluids don't conduct and and spread the misconception to students(which was reinforced by her when we argued).

I belive there should be a small mention of theese things for 1) The sake of avoiding misconception AND 2) For enhancing the curiosity of the students.

A single sentence mentioning of complex numbers in 10th grade by my favourite Math teacher bought Great curiosity in me.

One more thing to add, I have never seen it mentioned that conduction occurs in fluids explicitly in later classes but it was kind of assumed everyone knows. I wonder if there are students in my age who still belive It doesn't.