Though separated by thousands of miles, the two share secrets and discuss their favorite books, movie stars and cartoons through letters.

From Guo's letters, Semat, of No. 92 Middle School in Urumqi, learned of Shanghai's bustling commercial center of Lujiazui and developed a dream of one day studying in the metropolis.

The pair started their pen-pal friendship in July 2014, when the Communist Youth League (CYL) launched a program matchmaking students in Xinjiang with youngsters in other Chinese provinces and regions.

The CYL said on Wednesday that 2.8 million students from 7,338 primary and middle schools around China have been involved in the scheme, designed to encourage use of Mandarin and cultural understanding.

"Do you know Xinjiang has a butterfly valley?" wrote a primary school student from Altay Prefecture of Xinjiang to his pen friend in Jiamusi, northeast China's Heilongjiang Province.

Aynur Mahset, secretary of Xinjiang's regional CYL committee, said it encouraged students to share information on ethnic festivals, culture and activities in their letters, and that the pen-pals are also in touch with each other through more modern tools -- social messaging services like WeChat.

One year after the program was launched in Xinjiang, it was extended to Tibet, another remote corner of China where many people don't speak Mandarin. According to the CYL, 27,500 students from 570 primary schools in Tibet have established pen-pal relations with 189,500 students from 725 schools in 17 provinces and municipalities.

In 2015, the CYL also sponsored 52 summer camps in 17 provinces and municipalities as opportunities for the pen-pals to meet.

Although living in the same city of Urumqi, Aliman of the Uygur ethnic group and Wang Litong of the Han group, both sixth graders, got to know each other from writing letters under the CYL program. During the Spring Festival this week, Aliman visited Wang and brought her gifts of a Chinese knot and couplets on red paper.

Aliman said she knew Han people celebrated the festival with such decorations, but she didn't know their meaning.

China carries out bilingual education in Xinjiang and Tibet, enabling students to study both their native language and Mandarin. Promoting Mandarin, the official language of China, is meant to enhance mutual understanding and open up career opportunities for the ethnic groups in Xinjiang and Tibet.