That page (and the rest of the book) is far less pornographic than the actual porn I and many other kids I grew up with had access to, and regularly shared between ourselves, and is incredibly tame.

I also find it very telling that you'd consider what is on page 168 pornographic in the first place, sexually explicit maybe, but it is not intended to arouse or cause sexual excitement, it's meant to portray a lived experience.

The sexual repression in the United States is part of the reason why so many people grow up with the wrong ideas around sex and why teen pregnancy is such a big thing. Open discussion about these things (including gender and gender identity in that) is the best way to allow kids to grow up to be functional adults that are well informed and able to have critical thought about how and what they do and are far less likely to fall prey to predators and people who want to do them harm due to their lack of experience.