Most of the titles I thought of are ones that have already been mentioned.

At her age I was totally hooked on 'Wrinkle in Time' and the other books in that series. I also remember really liking 'From the Mixed Up Files of Mrs. Basil E. Frankweiler", "Jennifer, Hecate, Macbeth, William Mckinley and Me, Elizabeth", "The Westing Game" and the tripod trilogy by John Christopher.

The Witch of Blackbird Pond was another of my favorites, too!

I loved the Witch of Blackbird Pond, the Boxcar Children and A Wrinkle in Time! I have not read, but will find, Mixed Up Files, JHMWMandME, The Westing Game... and oh my goodness, the tripod trilogy. Our 7th Grade English teacher read those to us over the course of the year, and we moved before I found out the end. I obssessed over those books for years, trying to remember the title or the author or something.

I think I was reading Lloyd Alexander's Prydain books by that age. The first one, Book of Three, is very easy to absorb for a younger reader. Black Cauldron is (as the title might indicate) much darker, but one of the most compelling reads of my childhood.

I also just thought of Bunnicula and The Celery Stalks at midnight, and also John Bellairs books (The House with a Clock in its Walls, The Curse of the Blue Figureine), both of which I read at that age, and my friend K's son is currently reading, just going into third grade.

I just thought of those as well (eta: the Prydain Chronicles). I loved those books so much, still do.

Sophia, those sound like fun. I know I've run into Bunnicula, but not the others. My list is growing huge!

and Peter Pan and the StarCatchers -- the series is really good. my 4th grader made me read it All a prequel to the classic. and really well done.

Oh, that's right, beth-- that's the series that Dave Barry has written with Ridley Pearson. Nate has it, but I don't know that he ever got around to reading it. He's been completely hooked on The Warrior Heir and also The Extraordinary Adventures of Alfred Kropp which might be beyond K, but I know there are some people on the thread who might enjoy this for themselves:

Astonishingly tall 15-year-old Alfred is plunged into a world of adventure, assassination, and Arthurian legend when he agrees to help his uncle filch an ancient sword from the office of a CEO who just happens to be a descendent of the Knights of the Round Table. Of course the sword turns out to be none other than Excalibur, and the guy Alfred swiped it for is Mogart, a knight-gone-bad who hopes to use its magical powers to take over the world. Enter Bennacio, another descendant of the Round Table, who then takes Alfred under his wing on a quest across the Atlantic to rescue the sword from Mogart. The descriptions of minor bits of blood and gore leave much to the imagination and will make Kropp especially appealing to fans of Anthony Horowitz's Alex Rider books (Philomel), Geoffrey Huntington's Sorcerers of the Nightwing (ReganBooks, 2002), and even Darren Shan's The Saga of Darren Shan series (Little, Brown). True to its action-adventure genre, the story is lighthearted, entertaining, occasionally half-witted, but by and large fun.

Seconding or thirding the Prydain rec -- those books were among my very favorites as a kid.

If she has a taste for scary stories, she might like Mary Downing Hahn, who's written a bunch of ghost stories for younger readers. Some titles:

Wait Till Helen Comes
The Old Willis Place
Time For Andrew

I read several of hers around that age, I think, and loved them.

I loved the Witch of Blackbird Pond, the Boxcar Children and A Wrinkle in Time!

Me three.

What about Carry On, Mr. Bowditch? It is about being successful through math.