The difference between Ordinary and Extraordinary is
Middle School Tuba & Euphonium Resources
Fundamentals & Progressive Scale Study
Region 32 Resource Page
This year's music
Solo/Ensemble Resources for Tuba
This is a list, complied in 2020, of solos appropriate for a middle school tubist, ranging from beginner to advanced. Included next to each title are its range and rhythmic difficulty.
This is a much longer, but more comprehensive list of solos for both Middle School and High School Tubist, based on the ITEA Official Standard Literature List. You can find the original full list at the following link.
If you are interested in performing in an ensemble (in addition to your solo), follow the guide on this page.