Relatively
recently the JAA have taken a step towards a scientifically more correct (less
incorrect!) model for lift production.
This
applies Newton 3 and says that if the wing is experiencing an upwards force
then the airmass must experience a downwards force
and be deflected downwards, i.e. a change in direction.
(unfortunately this violates conservation of momentum, you
can never fully explain lift production with a two dimensional model, but it is
at least a step in the correct direction.)
To be
honest, lift production is a huge squirmy can of worms because a goodly
proportion of folk don't have the necessary Physics. Dubious science is
embedded in the industry, so your best bet is to just take it as read that
"lift production is due to a change in flow direction".
At high
speed with a lot of air passing over the wing a small downwash will give you
the lift you need. At low speed you need lots of downwash, and to get this you
need lots of alpha and lots of camber.
Once you
begin to look at lift like this all sorts of things become clearer, like
induced drag wing tip vortices and ground effect.
If you
want more information have a look at
http://www.allstar.fiu.edu/AERO/airflylvl3.htm