CLEVELAND, Ohio — For generations, children walked through the doors of the brick school sandwiched between West 10th Street and Tremont Avenue in one of Cleveland’s most vibrant neighborhoods. Now, as the Cleveland Metropolitan School District vacates the sprawling century-old building most recently known as Tremont Montessori, city leaders, neighborhood advocates and residents are beginning to imagine what comes next. Will the former school become housing? Community space? An arts destination?