Section 4. Every town containing, according to the latest federal census, five hundred families or householders, shall, unless specifically exempted by the board of education and under conditions defined by it, maintain a high school, adequately equipped, which shall be kept by a principal and such assistants as may be needed, of competent ability and good morals, who shall give instruction in such subjects as the school committee considers expedient. One or more courses of study, at least four years in length, shall be maintained in such high school and it shall be kept open for the benefit of all inhabitants of the town for at least the number of days required by said board, exclusive of vacations, in each school year; provided, however, that the date of graduation from such high school may precede the regular closing date of the school by not more than twelve school days. A school committee may determine that such school shall be conducted for less than the number of days required by said board in any year during which school has been closed because of epidemic, extraordinary weather conditions dangerous to the health or safety of pupils or other emergency, subject, however, to the provisions of section four A. Each high school maintained by a town required to belong to a superintendency union shall be conducted in accordance with standards of organization, equipment and instruction approved, from time to time, by the board.

Notwithstanding any general or special law to the contrary, school committees may award diplomas to any World War II veteran, Korean War veteran or Vietnam War veteran as defined in clause Forty-third of section 7 of chapter 4, who is a resident of the commonwealth, who attended the high school maintained by the school committee, who withdrew from secondary school before graduation in order to serve in the armed forces of the United States, who did not receive a high school diploma as a consequence of that service, and who was honorably discharged from the armed services. The department of education and the department of veterans' services shall jointly promulgate guidelines for the identification of eligible veterans by school districts and for the awarding of the diplomas by school committees.

Family members of deceased veterans, who otherwise are eligible to apply for the diplomas, may apply for a diploma for the veteran posthumously under the same guidelines set forth by the department of education and department of veterans services.