First Test (Book One of the Protector of the Small series) by Tamora Pierce
No Girls! Go Home! You Won't Last!
As Kel surveyed the damage done to her room-- mattresses, sheets, and blankets strewn everywhere, desk drawers dumped out onto the floor, wall hangings sliced with a glaive, and that message scrawled so plainly on the plaster walls, she knew the battle to be accepted as page was just beginning.