The Wizard's Hall (Paperback, 1st Magic carpet books ed)

Poor Henry. It's not enough that his mother has sent him away from home to learn magic. It's not enough that everyone at his new school calls him Thornmallow because he's "prickly on the outside, squishy within." It's not enough that the only talent he shows at Wizard's Hall is an ability to make messes of even the simplest spells. Now, when Wizard's Hall is threatened by a cruel sorcerer's fearsome beast, it is up to Henry--er, Thornmallow--to figure out how to save not only his new friends but also the entire school for wizards.