Giving a high school sectional

[MartyNeilan]

but I would like to see the low brass separated between trombones+baritones and tubas(+bass trombones) since the roles can be so different.

FWIW, high schools often do their sectionals as trombones together, and tubas/baritones together. Maybe good, maybe not, but that's how most band directors want them.

Which ever you do, I wouldn't dwell too much on the pedal tones. I have seen way too many fledgling tubists obsessive with trying to play pedal tones at all costs, and the rest of their notes sound like crap (and out of tune.)

[Stefan Kac]

The band director would probably appreciate it if your spent part of the time on their band music. To that end, it might make sense to group them based on their parts (i.e. who plays together the most, or who needs to work things out together in absence of the rest of the band).

[quinterbourne]

If you're a really cool guy doing stuff those kids really like and they enjoy the sectional, then maybe they'll want to take private lessons with you.

If you're not such a good guy and you just drill the band music like those crazy military guys you see in movies, then you could probably get a call back from the band director.

So, I think you should try to meet those two approaches in the middle. Be fun enough so that the kids like you, but improve their playing (both generally and in terms of performance of the band music) enough so the band director likes you. It's tough and it may take a few attempts to get the balance right...

[windshieldbug]

On the reverse side, this is a good, close, introduction to teaching (groups, not single students) for you. These are not adults, and will behave differently to different inputs. They are not interested enough to come to you, you came to them.

Do not let the students decide what to do for the majority of the sectional; save any democratic decision making for the last five minutes if they have been well behaved. You are expected to be the one in charge. The band director will anticipate a tight well disciplined rehearsal, within reasonable expectations. If he sees a free-for-all, you will probably not be coming back.

This is good advice, especially for high-school age kids. You are there to run a sectional, not look for customers.