Considering Maturity

I want to share all the amazing artwork I experience with my students. Unfortunately, I teach in an elementary school and there are some topics that are just not appropriate for this age range and environment: violence, nudity, sexuality, and heavily religious themes. 

These concepts, though rich with emotion and part of the human experience, can be too intense for young students. I want to protect my students from themes that are too mature for them, but I do not want to overlook important pieces that should be part of my art history curriculum. Should I ignore the underlying message from artists like Francis Bacon? Georgia O'Keefe? Andres Serrano? Is it respectful to discuss only surface representations and techniques? If I am to teach about the timeline of aesthetic beauty, how can I omit all nudity from my curriculum? 

I have a policy of sticking to the spirit in which an art piece was created, using primary source documents when possible and tend to cringe when art pieces, especially conceptual works, are watered down and taken at face value. As I challenge myself to introduce a more diverse range of artists and art movements, however, I find that I'm trying to construct ways in which I can appropriately frame artwork that I'd otherwise have to gloss over. How do you introduce mature topics in art with your students?