I've read (and enjoyed) most of these books. Another you might consider is the 100 Cupboards trilogy by N D Wilson. Mix between modern day rural America, and parallel worlds. Lovely. I would say it was written for a middle school audience, but I thoroughly enjoyed it as an adult.
I am reading your book, titled Circle of Magic: Sandry's book, and reminiscing over my school years. I felt tears come to my eyes as I was able to sincerely relate to the taunting and harassment that Briar (Roach), Tris, and Daja go through. Certain people can be cruel when they want to be, but I do know that it made me the strong young woman that I am today. They are still struggling while I move onwards and upwards, and I thank you for the inspiration you've given me as a writer. Meeting you took my breath away and I am grateful to have had the chance to do so. I hope to see you again someday, but if not, I will not forget you.
I read Defy yesterday, it kind of reminded me of Alanna: The First Adventure in that the main character has a twin brother and pretends to be a boy so she can go with him to the king's army. It wasn't as awesome as Alanna: The First Adventure, though. :(