Complex sentence: A decade earlier, the power of the Bureau of Indian Affairs had become so powerful that it almost destroyed many of the present tribal governments by trying to change and mold Indians to a non-Indian way of life through the schools themselves.
Split into simpler sentences: A decade earlier, the power of the Bureau of Indian Affairs had become so powerful that it almost destroyed many of the present tribal governments. One way the BIA did this was by trying to change and mold Indians to a non-Indian way of life through the schools themselves.