Leveling, like chair placements, is a little subjective, and (unlike chairs) maybe even unwise. Each state or division, or organization, has its own list and criteria, but words on paper hold very little significance in the performing arts. Even if a player says, "I can perform ________ ", how well did they actually play it? The skill list is a bit more objective than the listed works' titles.
Technique is not subjective, but other elements contribute to musical maturity as well. After teaching for several years, I've noticed how difficult it sometimes is to assign
just the right literature to each student. There should be a logical progression, but sometimes even deciding which piece is actually "harder than" another is quite challenging. For example, I'm not sure I agree with the ordinal placement of a few selections on Jenn's chart, but I still respect her teaching. On many ocassions, I've taught individuals whose technique far outpaces their cognitive skills, rhythmic comprehension (can the student subdivide tricky rhythms in an unfamiliar compound meter, in a slow, cerebral piece?), abstract thinking abilities, and perspective. Sometimes, the opposite is true. I've taught several extremely bright, diligent students who seek greater challenge, but sometimes lack the fingers and/or articulation to pull it all together. I have a student currently who's studying Beethoven sonatas and Chopin on the piano. Her musicianship is stupendous. Should I give her the Liebermann concerto? Uh, no. She'll need to stick with Mozart and Bach a bit longer. So who's on a higher level? The musicianship of the
latter group, I think--though they'll likely never perform the Dutilleux--is often better, but, of course, one needs to be a total package to perform challenging literature in a truly musical (as the composer might have imagined hearing the piece!) manner. The NFA pedagogy committee has prepared a VERY detailed skills list and literature guide, as a serious student might progress through the repertoire from elementary school through high school. It's available for purchase from their website ($3 or $5, or something insane like that). It doesn't include some of the most difficult literature, because, Pete's Sake, some things should be savored later, with more maturity. As well, even if high school students have enough technique and perspective to delve into those works, time is limited, and there are other things that should come first, as a foundation to all the rest. It's hard, psychologically, to catch up later. When you already have tons of technique, great tone, etc., digging back into mid-level literature makes you feel demoted, if you haven't progressed more logically. Just put one foot in front of the other, musically speaking, and you'll get to the next "level", whatever that is, when you get there.
Oh...FTR, I've performed most of the pieces listed at each level, to 10.