TubeNet

If they are little little, the smallest size yamahas, especially the older front action ones no longer made, work great.

In my School program, we start Instrumental music in 6th grade.
Over the last several years, I have "collected" several different tubas to help fit the size of the kids.
Smallest with a surprisingly nice sound, Besson "2-20"/"Stratford"( It's the one with a strage looking 3rd valve wrap, also marketed as an over the shoulder marching tuba)
small 3/4 size, 13" bell, .67? bore but heavy.
As mentioned before, YBB 103 Light and small. with front action valves.
(Schlepp beat me out of one on FLeaBay)
Small 4/4 Old's 0-99/Reynolds/Bach clone. This what most of the 8th Grade students play as they have finally grown into this size horn. (still with a .67? bore. )
Joe's Schafer tuba should fit in for smaller kids, I have an older King 1140
here as well.
YBB 102, school owns one, about the same size as 103. but a top action horn.
If funding becomes available, I'm trying to get either a Weril 4V(690?) or Jupiter 4V (482?)
Hope this helps,
Dave Hayami

There are a couple of the older Olds 3-valves, for some reason, in the basement of my undergrad. I have written a letter to the department chair, who I did go to undergrad with, about donating them to a middle school. She has not responded, and I'd like to think I can add the word "yet" to the end of this sentence.