LINCOLN, Neb. (AP) – Nebraska Gov. Dave Heineman and several key lawmakers say they’re considering a proposal to close a loophole in state law that lets 16- and 17-year-olds drop out of school with a parent’s permission.  Heineman says he has talked with Omaha Sen. Brad Ashford about a possible bill when lawmakers reconvene in January.  The U.S. Department of Education says that, as of last year, Nebraska was one of 21 states to require student attendance until age 18. But Sen. Greg Adams of York, chairman of the Legislature’s Education Committee, says the law also allows students to stop attending at age 16 with a parent’s notarized consent.  Ashford says that provision seems counterproductive, given Nebraska’s recent efforts to reduce truancy.