We also put Julia in school one year behind her age - we put her in Kinder when she was 6 1/2. She has progressed quite a bit, and I attribute that to lots of things, largely (1) desire to communicate at home w/her three sisters (get a word in at all!) and (2) desire to make friends at school. Her language exploded when she hit public school.
See this video clip taken almost exactly a year ago, when she'd been home a month and had lost her first tooth:
YouTube - tell me all about it kiddo
Now see her last Sunday,describing a recent trip to Houston to be with her cousins:
The Woodworth Family in Beautiful San Antonio TX
San Antonio has been hit with a cricket infestation lately. Tonight at Chick-Fil-A, she told me, "Mom, this is cricket city." Wow!
Is Anna around other kids a lot? I think desire to communicate really propels them.