As we know—Indians did NOT vanish and Curtis’s insistence on portraying Indians as living in an untouched past (including possibly retouching some of the photographs in order to remove modern objects) is troubling, to say the least.
On the other hand, Curtis did succeed in capturing the likeness of many important and well-known Indian people of that time, including Geronimo, Chief Joseph, Red Cloud, Medicine Crow and others. And many Indian scholars, including former director of the National Museum of the American Indian George Horse Capture, admire Curtis’s work.
Which leaves a question: How, if at all, should you use Curtis photographs in the classroom? There are tools to help.
The Eastman House has produced useful material on "The Vanishing Indian" with a special focus on the work of photographer Edward Curtis (http://education.eastmanhouse.org/discover/kits/files/9/ConsiderThese.pdf) as part of its "Discovery Kit" Beyond the Image: Depicting Native Americans.
The Library of Congress, which has over 2,000 Curtis images, gathered background information, including timelines, historical critiques, maps, and other relevant material for teachers in “Edward S. Curtis's The North American Indian: Photographic Images.”
Whether or not one ends up using Curtis photographs (and we chose not to, when we produced our textbook), the above links are worth reading to increase your own understanding about media portrayals of Indians. They provide lots to think about—not just about Curtis, but about portrayals of Indians generally, and about photography as a documentary art form.