@drabarni First thing, it's horrendously expensive but there are merit-based scholarships as well as needs-based. You are talking probably 4-5 times as expensive as the UK without scholarships: the top conservatoires are as expensive as the top US universities. Second, it's pretty crucial to distinguish between the conservatories, where it's non-stop music, and a music degree at the US universities, where half of your time MUST cover non-music subjects. Third, the level of theory in the US, per a very useful professor in one of the conservatories, on entry, is much, much lower than the UK - in Easter of Y12, DD was already doing theory equivalent to the 3rd year of the conservatory (though she has G6 Theory and is doing A-level Music and Maths).
That all said, we are lucky enough to be able to have spent time visiting the Conservatories and arranging test lessons with professors there. It's a huge commitment just to do the research.
The US timescale doesn't fit with UCAS conservatoires. Though we've had two calls to audition, we won't find out about the other two till end Jan and end Feb respectively. DD has had to accept the Glasgow waitlist place so as not to lose that, but she won't have a definite offer/decline from the US till March. That's unhelpful, and if we do pull out of Glasgow it's a little less easy than I'd like, though it's not a firm offer so they can't fuss much.
Application deadlines are end November, and the requirements are much more complex than UK - DD has four full compositions of which 3 are 4-5 minutes each; plus two essays for three of the four places, all on different subjects (what's your career ambition, why this place, how do you define artistic integrity); she had to do a short video intro to herself, a short video on a composer who inspired her; send a "transcript" which is a specific form of academic record; two references for each place, one academic and one musical... and every one was slightly different. Some require parental financial info up front, some don't require it at all, some need it only if you're called for audition.
The auditions she has are in person, so we will be scooting off to the US at least twice, hopefully 3 times (the fourth does not audition for composition, but does for other disciplines).
Our view was: if you can't get into one of these, you shouldn't cough up for the US. She's applied for the four best by ranking, but I wouldn't lay out this much money if she isn't that good. Also, she won't get a job in music if she isn't. There have been blunt discussions, which DD is cool with; and we have a back up plan if it doesn't work out.
I would start with the rankings of the global conservatoires, and then see which ones offer your DC's preferred instrument/composition/ music industry/music teaching options. Then look very closely at their websites - the costs are on each, as are useful things like how many years residency in halls they have! Accommodation is expensive outside halls. Some websites are rather offputting, but when we visited, even those institutions with websites of pompous pretentiousness were actually really down to earth and nice.
You might find the Sutton Trust helpful - they have a programme for state school applicants to the US (we didn't qualify).