i have been playing for 12 years done my exams and, i do well, play big pieces, practice scales half an hour every day, my piano has stiff keys so my fingers get a good workout, but the biggest problem is my fingers just dont move, how can i strengthen my fingers? is it the way i practice my scales? do i practice them wrong? my teacher wont let me do any etudes until i can play my scales properly 
HELP!
If you have been playing for 12 years you have to have good technique, have a good contact with keyboard, and have "fast" fingers. The first thing comes to mind is that you most probably do something wrong practicing, and most likely your whole approach to technique should be rethought.
There are many different schools of technique and many different approaches. I am for one who believes in technique as a mental process--all technique is in ones head. And the most important thing is complete relaxation of all muscles. The finger strength is not a gross muscular strength, but ability to focus energy at very short moment of taking sound--some talented and well tought little kids can have more sound and velocity than some adults.
For the beginning I'd suggest you to make a few excesises. First, try to analyze very carefully what happens when you throw a stone. You will see that your hand is "naturally" relaxed all the time, except of very short moment right before the stone leaving your hand, when your hand gets maximum velocity. Right after that your hand falls down, completely relaxed.
Now try to do exactly the same on the keyboard. Put one hand on the keyboard (5 finger pattern). You should feel very relaxed and comfortable. Lift one finger as high as you can. All other fingers should be relaxed and feel comfortable. then lightly, but very energetically drop the finger into the key. As soon as the finger hits the bottom, immediately remove all the pressure, leaving only as much, as it is enough to hold the key down. Basically, you should feel that hitting the key and relaxation is the same. Once you hit the bottom, all other fingers should rest on the keys (esp. pinkie!). Any, even 1mm gap between your finger and key surface, means that there is some tension--not good. Still holding this key, lift the next finger and repeat the process. Once you hit the next key, the first finger should release the note. If other fingers "want to follow" the one you lift (esp. when you work with 3-4-5) let them do it--never strain your hand. Do it slowly, concentraiting only on very big sound, maximum velocity and lighteness of dropping finger, immediate relaxation, and most of all, feeling completely comfortable all the time. Do it hands separately. When you get used to this feeling, try a little bit faster. When you get comfortable, once again, little faster, and try to put it into rhythm. Very often it helps to say aloud in very strict rhythm "lift-play-lift-play". You should say it very shortly. At this point, already lift the finger with the same velocity, as if you drop it, and remember two things:
1) At all times, except when you lift the finger, all the finger should rest on the keys.
2) Hitting the bottom, and relaxation are the same.
When you feel very comfortable with that, try to play exactly the same way a scale, learn every passage in your pieces, etc., and start putting your hands together, with exactly the same feeling.
When it becomes your "second nature" try to do exactly the same, but now without lifting fingers--right from the key surface. Your strokes will be much shorter, but the feeling of immediate relaxation should be the same. Hope it helps.