D.C. Mayor Marion Barry and a coalition of city officials and residents yesterday filed two challenges to the District's education tax credit initiative, alleging its supporters have misled the public and that it would cost the city far more than first thought.

The challenges were filed on the last day to ask the Board of Elections and Ethics to rule against putting the initiative on the November ballot. Both challenges made the same objections.

Foremost among them was the contention that the summary statement on petitions signed by citizens to call for the initiative was inaccurate in its alleged assertion that the proposed tax credit is limited to $1,200 per pupil.

The challengers argue that under the tax credit proposal no individual taxpayer can claim a credit of greater than $1,200 for each student. But, they contend, more than one taxpayer could, under the language of the proposal, claim a credit of up to $1,200 for expenses incurred on behalf of the same student.

An attorney who is a member of the group that drafted the initiative acknowledged yesterday that the measure's wording "was not explicit," but maintained the intent was to limit the total credit for each pupil to $1,200.

D.C. Council member Betty Ann Kane (At large), who opposes the linitiative, yesterday gave the following example of how she said the tax credit plan could work:

"Suppose Mary Jones has a daughter who goes to private school where the tuition is $3,600 and she is in the $25,000 tax bracket [in which she automatically owes the District $1,200 in taxes]. Mary Jones could contribute $1,200 toward her daughter's education and get a $1,200 tax credit." And says Kane, under the law, the student's grandmother, and even one of Mary Jones' neighbors could also each contribute $1,200 toward the girl's education and each receive the $1,200 credit.

The total education tax credit for the Jones family would be $3,600, Kane said. Thus, the District would actually be subsidizing the total cost of private school education for some families, she said.

However, Jule Herbert, a D.C. attorney who helped draft the initiative for the D.C. Committee for Improved Education, said in an interview yesterday after the challenges were filed that the petitions circulated to the public clearly stated that the total amount of credit per child would be $1,200.

The tax credit also could be claimed by people who send their children to the public schools, according to the initiative. The challenge filed by the mayor said there are 127,000 resident students in D.C. and that if a single tax credit of $1,200 was claimed for each student, the loss in revenue to the city would be $150 million.

"If the tax credit were taken by two taxpayers for each eligible student, the revenue loss would be $300 million," the mayor's challenge said.

In addition, both challenges said some of the people who circulated the initiative petitions were not registered voters in the District as the law requires.