NEWTOWN — School officials left a Saturday morning retreat still considering how best to tackle declining school enrollment, a trend that has re-opened discussions about closing an elementary school. Much of Saturday’s meeting focused on whether Superintendent Joe Erardi should further study shuttering a school— and idea heavily debated and ultimately tabled last summer — or if reconfiguring the district’s facilities could open space for municipal use, an early childhood education center or other options. Newtown’s school population, like many districts in western Connecticut and across the state, has dropped steadily in recent years. While no members said they favor a school closure, Alexander and Erardi were skeptical about the long-term accuracy of the study, which considers economic outlook, birthrates and other factors in its predictions.