When US President Donald Trump showed the video of his granddaughter singing and reciting poems in Mandarin to President Xi Jinping during Trump's visit to China last week, it became a hit on social media and prompted an outpouring of affection from many in China.

What the video of 5-year-old Arabella Kushner didn't show is the growing movement by many American families to have their children study Mandarin at a young age.

"We were so thrilled to see Arabella on social media. It was a surprise for everyone, and it's such a wonderful compliment to their parents," said Patrizia Saraceni Corman, founder and president of Carousel of Languages, a private language school in Manhattan where Ivanka Trump's three children studied Mandarin.

She said that the children came to the school several times each week over the past few years. "Theodore started when he was 4 months old - that's the most productive time that you can see tremendous progress," Corman said.

She said the school has seen a major increase in American families having their children learn Mandarin, and now there are more than 100 at the school.

"It's a huge investment in their children's future, not only because of China's emerging market, but Mandarin is an attractive language - children love to learn Mandarin because it's such a tonal language, and it is the language with the most native speakers in the world," Corman said.

She said the families learning Mandarin at the school are from all over the world, and they are there for various reasons. There are families where one or both parents are from China, who want their children to keep their cultural heritage, and there are American families who are attracted by their interest in China and its culture.

"Americans have completely changed their outlook about learning foreign languages, and we have seen an enormous shift with our American families and having their children start learning foreign languages as young as four months," said Corman.

Besides Ivanka Trump, many wealthy parents are also pushing their young children to learn Mandarin, including, according to Business Insider, Amazon founder Jeff Bezos and his wife MacKenzie, and Facebook CEO Mark Zuckerberg and his wife, Priscilla Chan.

When people ask Corman how to teach an infant Mandarin, "it's just exactly the way any parents teach their kids," she said, explaining that the school has created its teaching system based on a multi-sensory approach - verbal, visual and tactile association, that allows children to learn on multiple levels.

"I've taught infants, toddlers and young children Mandarin at the school. The kids came here are from 6 months to 12 years old," said Zhao Danchen, the head of curriculum design at the Carousel of Languages, whose students have included Arabella.

"When you teach a baby, she's 9 months, and she doesn't even speak English; all you need to do is to have her or him immersed in the whole-language environment. They are listening to you, they look at all the pops, the touch things, they hear you repeating the language, so they pick up right away, just like you learn Chinese in China," said Zhao, who graduated from Teachers College at Columbia University last year.

"The most interesting part about Mandarin is it's such a very different language; it has different characters, different pronunciation and tones, and they love writing. They regard Chinese as pictures, as kids love drawing, they love writing Chinese characters," she said.

"My husband and I lived in Hong Kong almost 10 years ago and are fascinated with how dynamic China was at that point and continues to be," said Erin Dillard, a mother of two students at Carousel who are learning Mandarin.