Section 81A. The board shall upon the request of any school for nurses or for practical nurses in the commonwealth inspect said school and notify its trustees or other governing body if said school is approved for the purposes of section seventy-four or seventy-four A, as the case may be, and, if not, what steps said school should take in order to gain the approval of the board. It shall from time to time inspect any school already approved and may withdraw its approval thereof. Said board shall notify the trustees or other governing body of each school if it merits continuance of approval, and, if not, may specify what steps the school should take to receive continuance of approval. Said board may make inspections by any of its members or by an agent or agents designated by it for the purpose, and no approval shall be withdrawn unless an inspection has been made. Any such trustees or other governing body aggrieved by an adverse decision of the board shall, on petition, be given a hearing before said board.