Is Jiang Guoji a teacher in Tang Junqiao?

No. Professor Tang Junqiao is a famous bamboo flute player and educator, and Mr. Jiang Guoji is the first person to play the flute with a smile in China. Both of them are flute masters, not teachers and students. Two master flute teachers are honorifics for teachers, who generally teach culture and technology or are worth learning in some ways.