How does one begin to thank a teacher?

I made this piece for Mrs. Palow, who has taught one, and sometimes two, of my children over the past six years. I cannot express what she has done for my kids and how much I adore her. This was a canvas board I'd painted some time ago. I collaged it for her, wrote a letter and added it to an envelope  glued on the back.

The door is inspired by one done in a Fat Book swap some years ago. The door is from Altered Pages and it's oil pastels for color.

How can one begin to thank someone who touches lives and open doors the way she does?