If you are often looking for visual supports for your subject areas, you will enjoy this site. The images address many time periods and cover many subjects. I would not let students look on their own since there are some nudes in the collection (after all, it is art). Instead, I would select images that could be used as an inspiration for writing, or background on a historical periods (ex. roaring twenties in the US right before the Wall Street Crash).
The instructions for its use are fairly easy to follow. Basically, as you zoom in with your mouse or touch pad, the picture you are focusing on becomes larger. Information on the painting or photo appears on the right side of the screen. I would hook my computer or iPad to my LCD projector and then I would have total control over the images my students would see. If you wish your students to look on their own, you may want parental permission since a few do address the beauty of the human body (and you know how immature some teenagers can be).
If you are an art teacher, you will want to bookmark this site for use in your classes. This would augment your instruction and motivate students to possibly entertain earning a degree in art! You never know:)
SAN FRANCISCO MUSEUM OF MODERN ART
ELL TEACHER PROS