Here’s a clip from a Hiroshima elementary school Band Festival. These young kids play with the tone, intonation, and even choreography of many high school bands.
It certainly appears they’ve had instruction on how to play the trumpet and other brass and percussion instruments. Asian educational systems are commonly very demanding of perfection, as is evident in this formal performance. Almost certainly the students have had some individual instruction. The song isn’t technically demanding, but shows a clear concetration on fundamental techniques of the trumpet and other instruments.