Schools should not be using sexually explicit content at all.
It is not necessary for children to (a) be able to explore absolutely anything sexually, and then (b) have those thoughts affirmed in their school library, curriculum, or any other literature used in the schools.
Materials that in photographic form would be pornographic, obscene, or illegal should not be allowed in schools just because the form of that content is drawn as a cartoon or other less realistic form. Its message remains, and it is wrong to push that kind of message on children or allow it in schools.
No lists of instructional materials with sexually explicit content should be accessible to students in any form at any time.
Any parent should have access to any and all instructional materials, including being able to attend any class at any time whether their children are part of that class or not.
Parents should receive notice any time any sexually-related content is used in any class or with their children at any time, explicit or not.
Parental notification should never be dependent on attending parent meetings at the school.
If sexually explicit material can be identified anywhere in schools, it should be banned and disciplinary action taken with whoever was responsible, students or staff. Parents should be notified it was identified and that it was banned.
If standardized national or state assessments use sexually explicit content, then the school system should abandon those testing systems entirely and permanently. That is inexcusable.