The D.C. Board of Elections and Ethics has rejected an attempt by City Council Chairman Arrington L. Dixon to keep a referendum on educational tax credits off the November ballot.

Dixon, leader of an ad hoc coalition of city officials and community leaders opposing the tax initiative, said yesterday that his group would appeal the board's ruling and promised that more challenges to the initiative would be made.

The board's decision was disclosed in a letter sent to Dixon Tuesday by elections board chairman Albert J. Beveridge. The Letter informed Dixon that the board's decision was based on a legal opinion provided by its attorney.

Backers of the initiative said yesterday that all that now stands in the way of the referendum taking place is a ruling by the board on the authenticity of the signatures on petitions backing the referendum.

Dixon had charged that the petitions filed in support of the initiative, which would allow taxpayers to claim up to $1,200 for each child attending a public or private District school, were invalid since the woman who notarized all the petitions also coordinated the initiative drive. Dixon said that the double role was a conflict of interest and a violation of city law.

But William H. Lewis, the elections board's general counsel, said that the restriction on who can and cannot notarize documents applies only to persons doing business with departments of the U.S. government.

Bill Keyes, a 27-year-old congressional staff member who is chairman of the D.C. Committee for Improved Education, sponsor of the initiative, said he was not worried about further challenges. "What are they going to fight us on? I think they're only hurting their own case," he said.

The educational tax credit idea, first proposed by Libertarian Ed Clark, would allow parents to deduct all educational expenses from their District of Columbia income tax up to $1,200 for each pupil in school. Deductible expenses include tuition, books, transportation and fees for special programs, such as remedial reading classes.

City officials have claimed that the deductions from local taxes would erode the city's tax base and strip up to $30 million from the city government's treasury.