In a proceeding pursuant to CPLR article 78 to compel disclosure of preliminary contract proposals and demands between the respondent board of education and its teachers association, petitioner appeals from a judgment of the Supreme Court, Suffolk County, dated August 24, 1978, which dismissed the petition. Judgment affirmed, without costs or disbursements. The affidavits of the district principal and the chief negotiator of the board of education provide substantive explanations as to why, in their opinion, disclosure of the requested information would impede ongoing collective bargaining negotiations. These reasons appear neither arbitrary nor capricious, and, hence, Special Term properly concluded that, based upon the expertise of the board’s affiants, the burden of proving the material exempt had been met (see Public Officers Law, § 87, subd 2, par [c]; § 89, subd 4, par [b]). Titone, J. P., Mangan o, Martuscello and O’Connor, JJ., concur.