I had the same situation... originally, I had an old yamaha upright, and when I switched teachers my new teacher had a 6'3'' Yamaha Grand. Of course, the touch is way different, and I couldn't play anything the same as at home. I ended up buying a piano similar to my teachers, a 5'8'' yamaha grand. Now, I can play much better at my lesson.
now, for your situation,,,you have a piano with heavy touch,,,your teacher has a piano with light touch...hmmm it would probably be better the other way around, that way you could practice on a piano with poor control and come to the lesson and play extraordinarily.
but..
YOU have the piano with heavy touch..
hmmm.
could it be nerves of playing a piano you aren't used to, in front of a teacher? I hope it is, because if it truly is a problem associated with playing very different pianos at home and at lessons, well, I feel sorry for you.
Maybe you could schedule time to practice at the lesson before the lesson to familiarize yourself with everything.
I feel so sorry for you, really. I know what it is like to practice hard every week, and come to the lesson looking like you haven't done anything. the teacher is angry, blames you for everything..
donjuan