Classical Dressage is my passion. One of my two Andalusians is now in training with an outstanding classical trainer and I'm thrilled with what's being taught to him - Firstly, to RELAX, then to carry himself in the most natural way for his bred: Light and Up in the front, with lifted back and lower haunches and rear legs reaching under. This is normally an advanced dressage shape (very collected) but Andalusians have been bred for hundreds of years to carry themselves this way naturally, so they do not need to be ridden "forward and down" for several years (going against what is natural for them), before they are taught to "collect". They are more comfortable in a collected shape from the start and that is what they are encouraging my horse to do, first by a specific type of lunging, then with various riding exercises.
Meanwhile, the trainer has encouraged me to work with my second Andalusian myself, to reteach him his own natural "collection". My second Andy is 13yo and has had quite a bit of dressage training already, and is very happy and willing, but it appears that he was trained more in the "warmblood" style and not encouraged to collect by rounding his back up and bringing his haunches under him. Warmbloods (and most modern style dressage horses) and usually not taught to truly "collect" until they are several years into their training program. This can be bad for an Andy.
If you can take advantage of the Classical training at your barn, do it. Your horse will thank you.
If I have time tomorrow (after I get back from a Classical Dressage clinic), I'll post my favorite Classical dressage links and books.
Classical Dressage encourages a relaxed, happy horse who is going in an easy, balanced manner.