Every school district and every area career and technical school, regardless of classification, shall be paid by the Commonwealth for every school year, on account of approved career and technical extension classes and pre-employment training, eighty per cent (80%) of the sum which was expended by the district or area career and technical school for the compensation of career and technical extension and pre-employment training teachers and supervisors. For the purpose of computing reimbursement, the maximum compensation shall be four dollars ($4.00) per hour for the 1985-1986 through the 1989-1990 school years and eight dollars and sixty cents ($8.60) per hour for the 1990-1991 school year and each school year thereafter and the amount expended for supervisory salaries shall not exceed twenty per cent (20%) of the sum expended for teachers' salaries: Provided, That in special cases when travel time or unusual preparation of instructional materials or other factors result in an inadequate compensation, the Department of Education may approve additional reimbursable employment time for such additional services upon the submission of adequate substantiative evidence from the responsible superintendent of schools. For the 1985-1986 school year and each school year thereafter, the Commonwealth shall pay the amount required by this section to the school district or area career and technical school which provided the approved career and technical extension classes and pre-employment training for which reimbursement is made.