Diane Sawyer on the Pine Ridge Indian Reservation Diane Sawyer visiting the neighborhood of Tashina Iron Horse, 5, on the Pine Ridge Indian Reservation. Tune in Friday at 10 p.m. ET for a special "20/20" with Diane Sawyer, "A Hidden America: Children of the Plains" Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Tashina and her mother Bobbi sharing family photos with Diane Sawyer. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Growing up in one of the poorest counties in America – The Pine Ridge Indian Reservation – takes resilience. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Tashina's uncle Matthew showing his latest creation. He hand sews every beaded dress for Tashina's pow-wow dances. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Tashina's hand-made beaded dresses for her pow-wow dances hanging in the home she shares with her 18 other family members. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Diane Sawyer visiting the home of student council president and quarterback Robert Looks Twice, where he lives with his grandmother, uncle and eight cousins. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Blossom Jumping Eagle telling Diane Sawyer about her life on the Pine Ridge Indian Reservation. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation President John Yellow Bird Steele telling Diane Sawyer about some of the great leaders of his tribe. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Marnie White Wolf, principal of Wounded Knee School, giving Diane Sawyer a tour. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation A classroom of kindergarteners at Wounded Knee School singing native Lakota songs for Diane Sawyer. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation A class photo with Diane and the kindergarteners of Wounded Knee School. Tune in Friday at 10 p.m. ET for a special "20/20" with Diane Sawyer, "A Hidden America: Children of the Plains" Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation A cart is rolled onto the top of a hatch to prevent access to an asbestos-filled storage space at Wounded Knee School. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Louise Clifford, 12, with Diane Sawyer, riding up in the hills of the Pine Ridge Indian Reservation in South Dakota. Jill Belsley/ABC News

Diane Sawyer on the Pine Ridge Indian Reservation Louise Clifford and Diane Sawyer gallop through the snow of South Dakota. Jill Belsley/ABC News