The chairman of the D.C. City Council's education committee yesterday urged Mayor Marion Barry and the council to put an additional $15 million into the mayor's proposed budget for the city's public school next year, and said she would support higher income taxes if necessary.

The increase, if approved, would raise the public schools' operating budget to $333.4 million for fiscal 1984, just $2 million less than the amount requested by the school board. Barry, citing declining public school enrollment, has proposed $318.5 million, an increase of $12 million over the current school year.

"Education . . . is of such great importance that if sufficient revenues cannot be found within the current resources, those revenues should be expanded," wrote council member Hilda Mason (Statehood-At large), chairman of the education committee.

Mason suggested revenues could be raised by "an education surtax" levied against all District income taxes, "and through an additional tax bracket for upper-income residents . . . . " Mason did not disclose further details.

Barry could not be reached for comment on Mason's proposal. The plan was submitted to council Chairman David A. Clarke, who must review the measure before making his own recommendations to the council within the next few weeks.

School board President David H. Eaton, who testified in January for full funding of the board's $336.5 million request, has said privately that the board would not accept less than $330 million.

Sources within the mayor's office have said the likely funding level would be about $327 million to $329 million. The school budget has triggered an annual fight among Barry, the school board and the council.

Under the city charter, the mayor and the council have authority to set the overall budget for the schools, but the school board has sole authority over how that money is spent.

Barry has contended that the school board has not cut administrative costs, while school board members say that lower budget marks proposed by Barry endanger the progress made in academic standards over the past few years.

The only cut made by Mason in the school request was $2.9 million for additional custodial employes, which Mason said, "seems inappropriate in a year in which the board has stated that no programmatic increases are being made."

Mason recommended no change in the $60.8 million budget mark set by Barry for the University of the District of Columbia.