HARTFORD, Conn. (AP) — With huge percentages of students unplugged from distance learning, educators at schools around the country have been working to understand why. Some describe an urgent need to address impediments in case remote learning resumes in the fall, when the stakes will be raised by the return of formal grading and attendance tracking. In Hartford, Connecticut, where a school principal has been going door to door to speak with parents of children who have not been participating, she sees many of the reasons why. Internet service is unreliable. Parents are away at work. And some are uncomfortable with the technology.