The Department of Public Instruction shall have the power, and its duty shall be:
(k) To hold examinations in secondary school subjects, at suitable times and places, to be designated by the Superintendent of Public Instruction, for the determination of the fitness of applicants unable to present satisfactory certificates showing completion of secondary school courses, and to issue such certificates to those found proficient: Provided, That admission to such examinations shall be denied any applicant eighteen years of age or under regularly enrolled in an accredited secondary school, and no applicant eighteen years of age or under not enrolled in an accredited secondary school, shall be allowed to obtain more units of secondary school credits through such examinations, during any year, than could be carried during any year through enrollment in an accredited secondary school; and to authorize accredited secondary schools to hold similar examinations and grant similar certificates under rules, regulations and standards issued by the Department of Public Instruction. To establish and publish standards whereby the secondary education of any resident of Pennsylvania, who has not fully completed his or her studies in an accredited secondary school, but has otherwise completed educational studies of an equivalent standard, may be determined and evaluated. The department may, under rules and regulations issued by it, grant credits, certificates or diplomas for secondary school education for educational courses offered by--
(1) The military, naval or merchant marine services.(2) The Armed Forces Institute.(3) Evening or extension courses established by schools and colleges, accredited or approved by the Department of Public Instruction.(4) Institutions maintained by the Commonwealth. The Department of Public Instruction may, under rules and regulations issued by it, authorize accredited secondary schools to determine and evaluate secondary school subjects, grant credits, certificates and diplomas in like manner.