Four members of the D.C. City Council blocked approval yesterday of a proposed emergency bill that would provide for a citywide public vote May 1 to fill a vacancy on the city's Board of Education.

The school board asked for the public vote rather than choosing a new member by a vote of the Board of Education itself, as the law now provides. The council's emergency bill was introduced by Hilda H. Mason (Statehood-At Large), a former school board member.

The vacancy on the school board was caused by the election of Betty Ann Kane as an at-large member of the council. A special citywide election will be held May I to fill council vacancies created by the election of Marion Barry as mayor and Arrington L. Dixon as council chairman.

When Mason's emergency bill was called up for action yesterday, there were seven votes in favor and four opposed -- one vote short of the necessary two-thirds to adopt emergency legislation.

Opposed were Dixon, William R. Spaulding (D-Ward 5), Willie J. Hardy (D-Ward 7) and Jerry A. Moore Jr. (R-At Large). David A. Clarke (D-Ward 1) was absent. Dixon said he did not want to tamper with the election machinery on a one-time basis.