Same; refund to employee; voluntary retirement; payment to heirs, when

If any time any such board of education employee who is willing to continue is not re-employed or is discharged before the time when he or she would, under the provisions of this act, be entitled to a pension, then such employee shall be paid back at once the money he or she may have contributed under this act. Any such employee who shall retire voluntarily from the service shall receive a refund of one-half of the money he or she shall have contributed under this act. Should any such employee die before receiving any of the benefits or pensions by this act provided, the board of education shall pay to such employee's heirs or estate the full amount, without interest, which shall have been paid into such pension fund by said employee.