TromboneChat

My son is in his 2nd year of band. He’s been using my trombone from middle school and we’d like to upgrade to something that is high enough quality to take him through high school, but don’t know where to start.

What is a good high quality trombone for a high school level trombone player.

What is your old trombone?

If you really want to get him something new, a nice Yamaha with an F-attachment may be good.
Or a King 3B-F.
Or a Conn 88H.
Or a Bach 42 A, B, or T

But have him try out the horn first.
Also, if he has a private teacher, ask the teacher for help. If he has no private teacher, maybe that is where you should start.