This is not about censoring or banning books or materials.  It is just giving parents the opportunity to find out more about certain materials that may be presented in class.  Parents have the primary responsibility and role of educating their children, thus should have the right to know more about what is being taught to their children.  Then they can make informed decisions about opting out of exposing their children to objectionable materials.

Another comment made an excellent point and compared reading materials to movies (which have ratings).  Here's what she said about it:  "It can certainly be argued that the mental image of reading such material is at least as strong as the visual image in a movie. If a parent is "strongly urged to find out more" about a movie with these types of themes, then s/he should also be strongly urged to find out more about these themes in required reading lists defined by schools. This amendment is not banning any books, as some commentors seem to suggest, but about notifying parents about sensitive material in required reading."