This post from Matt Youglove, featured on Vandoren's website, is really what it is all about.
Intonation is one of my favorite pedagogical topics in music, particularly because I am most methodical about it, and, because it is one of those things that really differentiates one young band from the next.
This part really nails it:
My point here is not to say that there is a correct frequency with which to tune; in fact it’s the opposite. There is NO correct pitch. Being in tune simply means that the frequencies you are producing on your instrument are at an agreeable ratio with the pitches being produced below you (which also applies to solo players – the lower notes being ones that you have previously played and are still in the listeners ear). You must play in tune with yourself as well as with others. The human ear hears the upper of two disagreeing pitches as “out of tune.”
The solution offered is exactly what I do with my students:
For this reason, I make all my students use a droning device. My preference is the Boss DB-88 Dr. Beat Metronome (which is no longer on the market – the DB-90 is the new model). I plug this into a PA system in my office and make students play the associated full scale over at least 3 different notes (usually chromatically adjacent), stopping on each consonance until it is perfectly in tune. This usually takes students quite a while at first, but the dividends are worthwhile.