A school board, after investigation, due notice of hearing and hearing thereon, shall dismiss any teacher, although having the requisite certificate, who proves unfit to teach or whose services the board deems unprofitable to the school; and give to that teacher a certificate of dismissal and of the reasons for the dismissal, a copy of which the board shall retain. That dismissal shall not deprive the teacher of compensation for previous services.   [PL 1981, c. 693, §§ 5, 8 (NEW).]