New York City

In a large private garden in Manhattan, behind a grand New York City brownstone, a man in his 90s took the hand of a young girl who is not yet 12. The bridge between them, the man's son, the girl's father, stood at a distance, looking on.

"That was pure love," says Sandi Pei, the 60-year-old son of I.M. Pei, the architect who designed Hong Kong's Bank of China tower and the Pyramid at the Louvre, in Paris, France. "I wasn't quite sure whether Anna was leading my father or if he was leading her."

So what kind of teachers could a school get if it paid them US$125,000 a year?

An accomplished violist who infuses her music lessons with the neuroscience of why one needs to practise, and creatively worded instructions such as: "Pass the melody gently, as if it were a bowl of Jell-O." A self-described "explorer" from Arizona who spent three decades honing her craft at public, private, urban and rural schools. Two with Ivy League degrees.