At the close of each fiscal school year, the mayor of the city shall appoint one or more expert accountants, who shall examine the books, accounts and vouchers of the treasurer and all other departments of expenditure of the board of the metropolitan district and shall make due report thereof to the mayor and the board of education of the city. All the officers and employees of the board shall produce and submit to the accountants for examination all books, papers, documents, vouchers and accounts in their office belonging or pertaining to the office, and shall in every way assist the accountants in their work. In the report to be made by the accountants they may make any recommendation they deem proper as to the business methods of the officers and employees. A reasonable compensation for the services shall be paid by the board.