When should young people start playing a musical instrument? This is a great question and there are a lot of answers.
The most important thing is the desire to play an instrument, and if they have interest, then there will be signs of their interest.
This young girl is an amazing violinist for any age. Beautiful playing. https://www.youtube.com/watch?v=4H6BitFb9zw
William at Caranige Hall https://www.youtube.com/watch?v=oybU09RQUTs
Emma He https://www.youtube.com/watch?v=DQeC5i9c09M
Young clarinet player https://www.youtube.com/watch?v=Ud9rmKn8yQE
Girl Trumpet players Melissa Venema age 17 https://www.youtube.com/watch?v=DRrTujHaHis
https://www.youtube.com/watch?v=lz9Fwi9DadY
Even children around 6 or 7 could start playing a recorder for example: Listen to the young people and they will usually tell you they like music!
All young people are amazing and they all have a talent they should be able to develop.