Whenever in any school year the school register of any teacher, or other records of any school district are destroyed by conflagration or public calamity, preventing the teacher and school officers from making their annual reports in the usual manner and with accuracy, affidavits of the teacher, the school principals, or other officers of the school district, certifying as to the contents of the destroyed register or other records, shall be accepted by all school authorities for all school purposes appertaining to the school district, except that of average daily attendance.