Solfege

I took a six year old student this fall that had been training at the Yamaha Music school. She's all the six year old you could ever want: toothless smile, boundless energy, not much piano experience. Together we are exploring the magic of music.
Before Thanksgiving, I gave her a very easy Faber level 1 Christmas book to help with her reading. This book keeps her little hands close to around 5 notes in each hand and has all the six year old favorites.
She came back from her Thanksgiving break eager to play her Christmas book for me. Hopping on the bench, she turned to the page, and belted out, "Let's all sing together now!" I jumped right in, expecting lyrics "Rudolph the Red Nosed Reindeer", but quickly realized I was the only one singing those words!
She was singing "Do re do la fa re do...!" I have not sung or taught Solfege since my college days. Boy was I rusty! I didn't learn the "do re mi" of music in piano, but rather in choir in middle and high school, and in my major at college. It was slowly coming back when we moved on to the rest of her lesson.
Do any music teachers out there teach young ones solfege in private lessons?
The world has come to know it by the Sound of Music. I think it IS a very good place to start. Have a great weekend. I'm going to begin the holiday preparations for the studio.