Back when I was part of my school's wind band, we used to always tune to a concert Bb. Why do wind bands tune to a Bb rather than an A (as discussed here)?
I recall our director once vaguely explaining this as being related to the fact that A is a relatively "difficult" note (in some sense) for brass instruments to play and that this confounds tuning somehow. I'm not sure what exactly this means, though, never having played a brass instrument.
Auxiliary question: do professional wind bands also tune to Bb, or is this just something done for the benefit of younger/less-skilled instrumentalists?