It is still advanced for a 3rd year student for solo & ensemble purposes. Of course, it is less unusual than for a whole middle school band/orchestra to tackle level 5.
I think it is because they are on block schedule. Four classes A/B alternating days. The 6th grade band has band for a two period block every day. They have adjunct professors who come and work with entire sections as well as private lessons. I think they accomplish a ton that first year.
Then in seventh and eighth grade you have a block of band one day alternating with a block of either jazz band or a block of symphony orchestra. My son is in the symphony orchestra.