If you're okay with more YA...
Dragon's Bait by Vivian Vande Velde is great and a quick little read. I really like how narrow the scope and setting are; it's a refreshing break from the save-the-world epics that are standard for fantasy.
Dianna Wynne Jones' Chrestomanci series is funny, poignant, and handles child protagonists well with some surprisingly dark bits treated gracefully. They're a set of stand-alone but interrelated works, so you see a fascinating variety of worlds. One of them is even a (anti-)magic school. It's sort of like a less preachy Narnia :p
I haven't read all of Diane Duane's Young Wizards series, but I love those that I have. They've made me cry. It's a modern, urban fantasy setting and makes excellent use of technology in a magical universe.
As far as I'm concerned, certain YA fantasy books deserve to be considered classic as much as the adult counterpart. I hope you'll give these a look!
This sounds a little like Dragon's Bait by Vivian Vande Velde. Here is a link to it on Amazon.