District of Columbia public schools are likely to lose $1.9 million under a federal court ruling that barred the use of 1970 census data in distributing federal school aid for low-income children.

The preliminary injunction, issued last week by District Court Judge Norma Holloway Johnson, probably will mean aid cuts for all area suburban school systems except Prince George's County, where there should be a slight gain.

District and suburban school officials said they had made allowances for the cuts in their budgets for the upcoming school year.

The injunction was won by lawyers for New York, 10 other states and Puerto Rico, which would lose money if the 1970 data were used, but would gain if funds were distributed according to the 1980 census figures on children from families below the poverty line.

U.S. Education Secretary Terrel H. Bell said in mid-May that he would distribute $2.4 billion in aid for the 1982-83 school year based on the 1970 data because information from the 1980 census was not available.

On June 1, the Census Bureau gave the Education Department a preliminary county-by-county report on the number of children aged 5 to 17 in poor families. But Bell said he was told that detailed poverty data for most of the nation's 16,000 school districts probably would not be ready until next winter. The plaintiffs in the case say that the more specific information is not needed for state and county allocations.

If the 1980 census figures are used, 18 states and Puerto Rico will gain funds because their numbers of children at the poverty level increased during the decade. But the District and 32 states, including Maryland and Virginia, will lose because they had more children under the poverty line in 1970.

Although she did not make a final ruling, Johnson said it was likely that New York and the other plaintiffs would prevail. She said that under the program, generally called Title I, "the secretary has no license to distribute funds in a manner which totally frustrates the major goal . . . to direct funds to low-income children."

The aid program, which is the federal government's largest for public education, targets money to schools with concentrations of children from low-income families. The name of the program comes from the section of the 1965 education act that authorized the program. It was renamed Chapter I last year.

The Congressional Research Service estimates that the use of 1980 census data would cut Title I funds to Washington from $13.7 million to $11.8 million. The number of school-age children in the city from poverty-level families dropped 25 percent, or 9,341, during the decade.

Fairfax County would lose $23l,000, down to $1.5 million; Montgomery, $201,000, down to $1.9 million, and Arlington and Alexandria would have smaller reductions.

Prince George's County, the only major suburban school system in which the number of children in low-income families rose during the decade, would gain $46,000, for a total of $3.7 million. The number of children in low-income families increased by 279, or 2.7 percent, to 10,652.

Johnson noted that under a "hold harmless" clause enacted by Congress, every school district is guaranteed in 1982-83 at least 85 percent of the funds it received in the past year. She said that Bell is free to distribute this money immediately, but a spokesman said the secretary has not yet decided whether to do so.

Education Department officials filed notice Friday that they will appeal Johnson's order and asked Johnson for a stay, contending that her injunction would "wreak . . . havoc" by putting programs, teacher contracts and students "in limbo."

But a spokesman for the Fairfax County schools said the system already had budgeted a 20 percent cut, which President Reagan had sought but Congress rejected.

Anne Pitts, director of the Title I program in Washington, said District of Columbia schools anticipated a similar cut.