The US system is pretty standard. There are Six grades. 1 being the easiest and for beginners and 6 being the hardest and for professionals and extremely advanced high school and college students. The listings vary from list to list. And Trombone solos are generally graded harder than the same solo for Euphonium. The lists are comprised of graded solos and various ensembles. The main one is the New York list, the NYSSMA There are solos and ensembles for almost every instrument in it, from voice to timpani and even bass trombone.