So many variables. My kid’s high school had a top jazz program, essentially pro level training for 4 yrs. No way a private school could’ve matched that. I’ve never seen a private academic school at the Essentially Ellington competition - they’re all at least medium-sized public high schools, except for a few regional groups that draw upon many high schools (and really shouldn’t be competing against the single school groups).
Instrument. Those who are on their way to become professional soloists on strings or piano might practice 8 hours/day. At that level, many don’t go to school anymore, just do minimal homeschooling, so that they can devote more time to practicing. Certain other instruments, those that depend upon mouth embouchure, might be unable to practice more than 4 hours/day, and usually less, due to physical limitations.
Life. Many families feel that having a kid concentrate so exclusively on one activity is not good for the child’s socioemotional development - and they’re usually right.
If your child is thinking of doing music ed, they really don’t need to be practicing as if they were intent upon a position in the NY Philharmonic, or a solo career. Honestly, they’re better off learning to double on another related instrument, or picking up a completely unrelated instrument, especially if they’re thinking of elementary music ed, where they’d be expected to give lessons on multiple instruments. Most importantly, they should be doing it because they love playing various instruments, love music.
My kid was very successful with high school music, but as of yet seems to still be focused on medicine, although they still play a ton of music. When we totaled up the hours, we saw that they had been spending 40 hrs/wk on music, outside of school hours, throughout all of high school. Seemed to practice an hour twice daily, but also played a lot in school, too, but their instrument is impossible to practice more than 4 hrs daily, due to physical limitations. They probably could have gotten into any conservatory in the nation on a decent audition day, but decided to go to a tippy-top and didn’t apply for the dual degree program with the nearby conservatory. There is no way that they would have gotten into that school without their musical achievement.
If your kid wants a performance music program, then yes, they do need to be practicing more. But then again, every musician feels that they should be practicing more! If they want music ed, it’s less of an issue.