I know because I know the music teachers in the public schools. I have several friends who are or were (retired) music teachers in our public school system.
I also know because for the last ten years, I have chaired our city’s music scholarship competition, and I talk to the teachers and the parents. I have personally met with music teachers from the public schools and talked with them about the competition, and they have told me what their music curriculum consists of. And I talk to the students when I do get public school students in the competition, and they tell me that their musical education is obtained through private lessons, not school
I know from our local news reports (newspapers, radio, and television) that only in the last few years has band been restored to our public schools. There is still no orchestra program.
The meeting I referred to was a report on the state of the arts in our public schools (that’s why I attended the meeting, even though I’m not a school teacher–I am interested because of my position with the scholarship competition)… Written information was presented about the curricula in the schools.
It is getting better ,because as you and others know, musical training helps students develop critical thinking skills. There have been studies demonstrating that musical training helps a student with math skills, although I must say it never helped me with math. Oh, well–I guess I’m an outlier.

The problem is money–when something is cut, it WILL be music because it’s more important for the students to learn to read words than music. One reason the hip hop program was created was so that they classrooms could use current popular music instead of buying books and supplemental material, and maintaining a keyboard. Also, people who weren’t music teachers could teach it, because all they had to do was turn on the music and let the students dance along. That’s what STUDENTS told me–there was no teaching, just listening and dancing.
I have lived in my city most of my life and have been involved in many ways. I know what’s going on, especially in the music world here.