More than 1,000 unionized support staff workers in the North Penn School District have a restructured labor contract.   The school board approved it Tuesday night.   The settlement offers job security for the next three years in exchange for two six month pay freezes.   Without it, the school board was prepared to layoff 13 union members.   Every organized employee group in the district has accepted pay freezes except for the teachers.   The school board demoted 36 of them to cut costs after it was unable to reach an agreement with their union.