The owner of Lacaze-Gardner School, which closed last November after disclosures that the school was being investigated for possible abuse of federal student aid, has filed a $50 million suit against The Washington Post, seven other newsgathering organizations, and two news reporters.

Daniel A. Grossman filed the suit in D.C. Superior Court last Saturday on behalf of himself and his three solely owned corporations, Lacaze-Gardner School, Jacobs-Gardner Supply company and Sanz School.

In the 10-page suit, Grossman contended that he and his three corporations were held up to "public scorn, hatred, contempt and ridicule" as a result of "false, misleading, unsubstantitated and defamatory statements" that were either printed or broadcast about him and his businesses between Aug. 26, 1978, and May 1979.

Defendants in Grossman's suit are The Washington Post Company, The Washington Star Company, The evening News Association, Washington Radio, Inc., Metromedia, Inc., WJLA, Inc., National Broadcasting Company, Sonderling Broadcasting Company, Jonathan Fuerbringer, a staff writer for The Washington Star, and Joseph D. Whitaker, a staff writer for The Washington Post.

The Lacaze-Gardner School, a business school which primarily attracted a student body of inner-city youths, closed last November following a series of fires in school buildings and protests against the school by its students.

Since last September, Lacaze-Gardner has been under investigation in connection with allegations the school abused federal student aid programs.