It's dumb for me to keep this up because it comes across as a quibble and we're well beyond answering the OP's question. But it's a burr under my saddle. Forgive me. Let me start with a note to Someday -- if any part of this seems directed at you, it isn't. Props.
I don't know how anyone can make a hard and fast generalization about what culinary schools teach unless you've been to quite a few or are, in some other way, familiar with their curricula. Johnson and Wales, for instance, recommends hot milk into very warm roux (just off the fire, butter no longer bubbling). Julia Child's recipe was straight out of the Paris LCB school and it's hot into hot. I don't have the book with me, can't find it online, but IIRC LCB still teaches hot into hot. Don't they count? Aren't Johnson and Wales and LCB real cooking schools?
There are a lot of cold/hot/warm roux/milk permutations which work for bechamel, and a very few which don't. Some are better than others for certain purposes -- like speed, quantity or convenience -- but good technique will net you a smooth and velvety sauce with most of them.
Claiming ways which actually work quite well are less theoretically correct is silly. If you tell me your way works, I accept that; but if you tell me mine can't, won't or doesn't, that's disturbing.
Someday -- I get that you're talking about your experience in cooking school and respect that. Also, you're right about soubise. I misused the term; a result of a misunderstanding from when I started cooking at an old line French restaurant in SF thirty seven years ago; a place without a lot of English in the kitchen. The misuse sticks persistently even though I know better. I can't remember trig relationships either. Or lots of other things from back then. My drug use at the time has absolutely nothing to do with it.
Edited by boar_d_laze - 10/7/11 at 11:47am