A former Hudson middle school teacher pleaded not guilty Friday to charges she repeatedly raped a 13-year-old girl a decade ago after meeting her at the school where she worked and where the child was a seventh-grader. Caitlin Harding, 37, of Wellesley, was arraigned via Zoom in Middlesex Superior Court on one count of rape of a child by force, three counts of aggravated rape of a child, and six counts of indecent assault and battery of a child under 14.