The meetings of the school committee, except when in executive session, shall be open and accessible to the public. Final action shall be taken only in open meeting, except on disciplinary and other personal matters, the disclosure of which, in the opinion of the school committee would be detrimental to any pupil or member of the school department involved. Where the school committee considers the disclosure in such cases detrimental as aforesaid, its action shall be recorded separately and may be kept confidential and shall not be considered a public record.