That is a great point regarding competing interests at the high school level and dialing back if the situation warrants it. I have no intention of acting as a practice "Nazi" as I believe the choice should lie with them at that age. However, music lessons are expensive ($60 to $100+) where we live so I am not willing to expend that much weekly (times 2 for 2 kids) if they are not committed to improving. It is not that I would withhold lessons, just not provide 60-minute lessons with a distinguished musician. If they wanted to play for fun, 30 or 45 minutes with a teacher with a typical background is a reasonable compromise so that money can be used for something else.
What do your kids want - the "distinguished musician" or the "typical teacher?" What do they have now? Some distinguished musicians are terrible teachers and vice versa. My more serious musician has a less distinguished teacher than my less serious musician because of teacher-student chemistry. Serious musician daughter has had the same teacher since she started her instrument in fifth grade. They have wonderful chemistry and this teacher has been a fabulous mentor. Even though this teacher does not play in any of the "big name" symphonies or orchestras around here, she regularly has students receive scholarships to play in college. Less serious musician daughter recently switched teachers. She is now studying with a teacher who plays in the symphony and teaches at the university. This daughter had stagnated with her previous teacher and felt like she wasn't achieving her modest goals. She found the new teacher herself by talking to upperclassmen she respected and asking for recommendations. I wanted to support this rare bit of self-advocacy. It is costing me more but my daughter is more engaged and motivated than ever. Maybe she will become a more serious musician, maybe not.
Five hours of practice time would be difficult for either of my girls to commit to on a regular basis. Some weeks they have the time, some weeks they don't. They are both in an IB program that sometimes has a heavy homework load. Also, once they got to high school, they seemed to gravitate to a couple longer sessions every week instead of daily sessions. They have both made all-county and various university honor bands, though not all-state. They are on a block schedule at school so they have 3-4.5 hours of band at school plus 2 hours of an extra-curricular band every week, not to mention the extreme time commitment of the musical every spring. Even though they love their instruments, sometimes practice is the things that has to give.