Yes, all your students can start at a level best suited for them. After they have watched the introductory video in the first mission and optionally tuned their instrument, simply have them take a skill test (Try to Unlock level X) in the syllabus. Skills tests are designed to determine the skill level for each student. Upon successful completion of a skill test, all previous content in the syllabus will be automatically unlocked.
If a skill test is too hard, they should try an easier one. Conversely, if a skill test is too easy, they can play a harder one. This way, every student can find their level and progress from there.