Not only should sexually explicit content be made known to parents before being adopted in the school curriculum, the determination of what is explicit should be made by involved parents. Today's hyper-sexualized society allows things which should not be public. Parents are the ones who are in the best position to determine what each of their children should be taught, or to be shielded from.
Please also make sure through this document that there are certain specific actions that every school MUST take in order to ensure sexually explicit materials are correctly identified and seen by parents first. I am concerned that, unless certain minimum standards are expressly mandated (as opposed to providing examples or suggestions), many schools may find ways around what they consider to be mere guidance.