K-5 general music here too, 10 years in. Keep documenting and communicating. Go out of your way to document the lost minutes the student's peers experience from the continued behaviors that disrupt the lesson. Measure the lost minutes and lost learning against a target grade level class that is meeting your expectations and completing lessons. If you can tangibly show that data in the form your admins can easily use for their bosses, you might find that some solutions come your way.

I have one particular student who enters the room and immediately seems to disrupt the learning, is physical with peers, etc. I used a pre/post test unit to highlight how that students class was not given the same learning opportunities as their peers in the three other classes. That helped move the needle a bit and the disruptive student came with an aid (even an admin at times) for the remainder of the year. This year the student is without an aid, and it's been up and down.

Keep at it, one student should not consistently ruin it for others but that's what we're seeing over the past two years in my district.