Wang Ziyao, 18, said she had spent days preparing for the Iowan students' arrival, hoping to help them understand the story of friendship linking her school with Iowa.

What impressed her most, she said, was the eagerness with which the US students engaged. In weaving and martial arts classes, they listened closely, joined in enthusiastically and applauded the children performing at the start of the martial arts session. "You could really see how much they admired Chinese culture," she said.

For Wang, however, the emotional center of the day came in the school's Friendship Grove, where a ginkgo tree planted years ago by honorary principals Lande and Berrone has come to symbolize continuity across time and distance.

"Each time US students visit China, they hang their wishes on the tree, helping carry the friendship forward," she said.

Wang herself had experienced that continuity from both sides. After visiting Muscatine, Iowa, and Muscatine High School, she was able to reunite in Shijiazhuang with a US student she had met there the year before. "We saw each other again here in China and said, 'Long time no see,'" she said. "What had begun in Iowa had now come back to Hebei."

For others in the delegation, moments of unscripted delight also became part of what they would take home.

"This is my first time seeing a panda in my life," said Eric Yael Rodriguez-Alcaraz. "Seeing a panda in person is amazing." He said he had already been calling family and friends back home about what he had seen, and hoped one day to bring his family to China.