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