MARBLEHEAD – The School Department has told parents to expect more of a police presence in the schools this fall – and staff and visitors will wear visible identification.The changes represent a system-wide response to the discovery of a bullet at the high school last spring.In a letter to school parents, Superintendent Paul Dulac, Police Chief Robert Picariello and Fire Chief Barry Dixey said, “Periodically, you or your children may observe a uniformed police officer in the school or walking the grounds. There will also be occasions when non-uniformed officers are present in the schools.”The letter, which will be sent to each school parent and can be viewed at www.marblehead.com/schools/security, explained that the “unobtrusive” visits will also allow new officers to familiarize themselves with the school layouts.Schools are also securing all secondary doors so that people inside can leave the building but people outside can’t get in. Access to each school will be through a main entrance. School staff will wear ID badges and all visitors must report to the school office where they will receive visitor pases which they must wear at all times in the building.School officials are making an effort to communicate with parents this fall about school security.School Business Manager David Keniston told the School Committee Thursday evening that the schools are purchasing a new home alert system called Alert Now for $7,750. The system will be used to communicate with each student’s home by telephone or email, to announce snow days or more serious emergencies. It has the capability to send 1,000 messages a minute. Keniston said the schools will be updating their home contact information for each student.Dulac said the system had great potential for school-parent communication.