So.... how do I teach without using the term "arm weight"?
It's a bit like the old joke about the doctor who tells his patient, "If it hurts when you go like this, don't go like this." I just don't use the phrase. Done and done.
What is most important is that I help a student play with the best coordination possible, becoming sensitive to the spectrum of sounds he or she can create while working with the whole body's structure. This establishes a secure auditory/motor loop that a student can come back to with ease.
My recommendations:
1. Observe how your student moves in response to your choice of words. If you start to see tension rather than ease, find a new set of words that is more accurate and appropriate.
2. Ask your students how they think dynamics are produced, especially loud sounds. You may be surprised at what they think, despite what you have been teaching.
3. Use your technology to show your student movements that are getting in the way of comfortable, reliable performance strategies. A new app that is great for this is called Coach's Eye. It is designed for athletes, but it is ideal for music performance teaching.
4. Teach your students how the piano works. Many piano dealers have old action models they will give away for free. This is how I acquired mine. If you don't have an action model, show your students the inside of your piano. There are also YouTube videos of the parts of the action for grands and for uprights.
5. Study Body Mapping, Teaching the Art of Movement in Music. Information on this practical process can be found at www.bodymap.org.
6. Study movement education through Alexander Technique and Feldenkrais.
7. Share critical listening and observation skills with your students by watching videos and live performances together.
8. Model, model, model! Explore what happens to your own playing as you give up the idea of sending weight into the keys. For most pianists, it is extremely freeing, and it opens up more options for sound.