Some Danbury elementary school teachers moved into new portable classrooms over the weekend.  Shelter Rock School 4th graders moved into four new portables while 2nd grade teachers moved into the newly empty classrooms .  The second-grade classes were doubled up in one classroom – with 43 students in one room with two teachers. Now there are groups of 21 and 22 students, each in its own classroom.  Danbury School officials say enrollment at Shelter Rock School grew by about 550 students over the past few years, and despite five new classrooms being added two years ago, more space was needed this year.  The portables are connected to the school building through an enclosed hallway off the gym.