I have had 5th grade beginning band for several years. I am at a 3A school, also with 2 directors. I teach woodwinds. The other director teaches brass. We start flute, clarinet, trumpet, baritone, tuba, and sometimes trombone, depending on the students. We wait until 6th grade to start french horn, saxophone, and percussion. We wait until 7th grade to add oboe and bassoon.

There is a HUGE difference between 4th and 5th graders. 5th graders can handle band just fine. You may not notice a difference between 5th and 6th grade beginners until their advanced development in high school.