The school committee of the town of Cumberland in electing teachers shall elect to serve at its discretion all teachers who have served in the schools under its direction for the previous three (3) consecutive school years; provided, that the school committee of the town of Cumberland may elect to serve at its discretion any person who has served more than one previous consecutive year. The school committee of the town of Cumberland may dismiss a teacher within the year of employment in the instance of teachers not employed at discretion, and at any time in the instance of teachers employed at discretion by a two-thirds (?) vote of the whole school committee for cause, which may be a violation of law, flagrant or persistent violation of the rules and regulations legally prescribed by the school committee, inefficiency, incapacity, insubordination, conduct unbecoming a teacher, or other just cause; provided, that no teacher shall be dismissed unless he or she has received a written copy of the charge or charges against him or her not less than thirty (30) days before the meeting at which the charge or charges are to be considered, and unless the teacher if he or she so requests it has been given a hearing before the school committee, and unless the charge or charges has or have been admitted or substantiated; and provided, further, that nothing in this section shall prevent the retirement of any teacher under a rule of the school committee affecting marriage or for the purpose of chapter 15 of this title; or the retirement at the end of any school year of any teacher whose services may no longer be required by reason of the closing of schools or the discontinuance of classes; and provided, further, that the school committee of the town of Cumberland may suspend any teacher for cause pending a hearing, but that suspension shall not involve loss of salary unless the cause is sufficient to justify dismissal as provided in this section.