§ 8. Dual Classifications (applicable only to the Board of Education).

Where it is determined by the appointing authority, with the approval of the Commission, that it is frequently necessary for an employee to perform duties outside of his classification, such employee may be appointed to a class involving such duties and retain his original classification. Competitive examination shall be the means of selection for dual class if the position is of a higher level than the original classification, except as the Commission shall otherwise determine. Any subsequent full time vacancy in the higher classification shall be filled by the employee holding a dual classification with the highest seniority in that class and in the same employing unit. No employee may be made full time in any higher class unless his last service rating was at least "satisfactory."