There are two things that I think are worth highlighting in relation to the IFLA School Library Guidelines in this regard.
Firstly literacy and reading promotion needs to be approached from the definition of a school library, which is “a school’s physical and digital learning space where reading, inquiry, research, thinking, imagination, and creativity are central to students’ information-to-knowledge journey and to their personal, social, and cultural growth” (p. 16). There are 3 elements to this definition:
The school library is a physical and digital learning space, in which …
… reading, inquiry, research, thinking, imagination, and creativity are all means to an end …
… which is the information-to-knowledge journey and personal, social, and cultural growth of students.
It is important to root the discussion about reading for pleasure and reading for learning in this definition, I think, because the information-to-knowledge journey is simply not possible without reading, and this reading must be what you are calling reading for learning (although reading for pleasure can contribute to this journey). It is also worth noting that the definition lists reading along with inquiry, research, thinking, imagination, and creativity, but in reality it is difficult to imagine those activities separated from reading, even if only indirectly.
Secondly, “school library services include … [a] vibrant literature/reading program for academic achievement and personal enjoyment and enrichment” (p. 19). This states explicitly that the librarian’s role includes both reading for learning and reading for pleasure.
If by first part you mean establishing a case for reading for pleasure and reading for learning, then I don’t think that you can afford to rush this.
Also, what might a vibrant literature/reading program for academic achievement, rather than personal enjoyment and enrichment (which we, as librarians, are very comfortable with), look like?
I’m very interested to see where this part of the discussion leads.