BAY CITY, TX --Bay City ISD is warning all parents about the latest threat made against the school district. The school district says it's been notified by the Matagorda County District Attorney's Office that several businesses and private homes have received threatening phone calls from a blocked number, according to Bay City ISD's website. The call comes after two threatening letters demanding changes within Bay City ISD were sent to the district. During the holidays, a writer claiming to be the parent of a child sent the district letter threatening the superintendent's family and random students with violence unless nine specific rules are followed. Less than two weeks ago, a second letter was sent to the school district, and the district attorney's office says it appeared to have been written in the same style and manners as a previous letter. The caller on Wednesday cited a February 1 deadline for demands to be met or else students would be harmed.