What I would add to this list is given how nebulous the whole process is be very careful in generalizing too much. It could be in a music program in a university where academic merit will be awarded, you would know that for example let’s say a 2000+ SAT would get the kid more academic aid, then yeah if he/she got a 1900 it might be worth retaking the test to try and bring it up to that level…but what if you don’t really know where that kicks in?
In a sense in this kind of sitation there is a zero sum game between getting your playing up to the right level while maintaining academics high enough not just to get admitted, but to get academic merit aid as well…and for example, if you concentrate on the academic, and increase that side of things, what will happen to the playing, if you play well enough to get in but at a level it decreases or minimizes your music merit aid, you may end up actually losing, perhaps if the kid put more time in the music the merit aid from that side would have been greater than any lost aid on the academic side…and one thing I have seen up close with friend’s of my son, that the stress of trying to mantain the academic side, especially where they attempt all the AP classes and so forth, getting high test scores, hurt their playing ability, it happened time and again, kids heading more for the academic saw their playing fall off (there are always exceptions).
One thing I would recommend, which comes up here time and again, is if you are doing the music school in a university, to contact the admissions departments on both sides and ask the kind of criteria used for awards, especially on the academic side of things, while they likely would tell you that awards change from year to year, etc, they might be able to tell you that for example, their highest level of academic awards are given to kids who are in the top X percentile of the SAT, are above Y in unweighted GPA, in x position in their class…and even if they won’t/can’t tell you, it doesn’t hurt to try. The most frustrating thing about this whole process, music and academic sides, is just how non transparent much of it is. For example, in the OP’s case, did the kid not get into JHU because his academics were off enough, or did he not get in because he was doing a double degree and they felt for whatever reasons that he wouldn’t be able to do that (ie that if he had applied to JHU without the music school, maybe he would have gotten in).
Having gone through this in UG, and now going through it with my son applying to grad schools, one of the things I can tell you is that music is full of the regrets for ‘the road not taken’, even though we’ll never know in any kind of fact whether path2 would have been better than path1 (kind of like the road less travelled, where we convince ourselves that any path we took was the road less travelled and it turned out great lol).
To quote the great poet Robert Burns, talking about a mouse he had unearthed on plowing a field:
Still, thou art blest, compar’d wi’ me!
The present only toucheth thee:
But Och! I backward cast my e’e,
On prospects drear!
An’ forward, tho’ I canna see,
I guess an’ fear!