Complex sentence: A five-and a six-year-old were sent back to be educated with the Dalai Lama, the idea being that they would one day return to Mustang having had a Tibetan education.
Split into simpler sentences: A five-and a six-year-old were sent back to be educated with the Dalai Lama. The idea being that they would one day return to Mustang having had a Tibetan education.