Common Sense Media has a great page for teachers with a nice video, information, stats, tips for parents, etc when dealing with Sexting. This is not an all encompasing site with everything you need, however, it is a great starting point for researching, learning, discussing, and teaching about Sexting.
I recommend you preview the video and the information on Common Sense Media's Sexting Page before sharing it with your classroom. The video may be inappropriate for some students. In my classroom, I normally send a page home that mentions we are talking about sexting so my parents are aware.
Below, I have also linked 2 videos that detail stories of Sexting and where the consequences may lead. I have shared these stories with many of my students. Both are very heartbreaking and eye opening.
Jessie Logan's Sexting Story
Hope Witsell's Sexting Story