I agree, there should be no restrictions on this book for private purchase, but it should not be included in taxpayer-funded government school libraries. 

Since others are likely to agree, though, and you are seeking debate, here are some questions that might be a little tougher. 

Given taxpayer-funded libraries and schools exist and aren’t going away anytime soon:

What if this same book had no pictures, but explicitly described scenes in text?

What if this same book had no pictures, but described situations in text as non-explicitly as possible?

How about this book’s presence in a taxpayer-funded library that is not in a school?  Large libraries often contain erotica as well as children’s books in different sections, and kids are able to roam anywhere. 

How about this book’s presence in a privately-owned library or bookstore?  Again, bookstores often contain erotica as well as children’s books in different sections which are accessible to kids of all ages.