Washington is discounting the legislative chances of President Reagan's plan for federal aid to private and parochial schools -- even before he offers it.
As the administration seeks to balance the budget and limits federal educational aid in certain school categories, it will be difficult to get Congress to make tax credits available in a sensitive area that involves constitutional church-state questions.
The President is expected to make his proposal in a Thursday speech to the National Catholic Education Association.
As a presidential candidate, Mr. Reagan supported federal aid to private schools. The 1980 GOP platform charged that the Carter administration ''cruelly reneged'' on education aid promises made during the 1976 campaign. It declared that ''next year, a Republican White House will assist, not sabotage, congressional efforts to enact tuition tax relief into law.''
At Wheaton, Md., on Oct. 8, 1980, Mr. Reagan backed tuition tax credits to aid parents sending children to nonpublic schools.
Sen. Bob Dole (R) of Kansas, chairman of the Senate Finance Committee, and Rep. Barber R. Conable Jr. (R) of New York, ranking minority member of the House Ways and Means Committee -- who have supported tuition tax credits -- now think the Treasury deficit is too big to go ahead with them, according to aides.
On the other hand, a major supporter of tax credits, Sen. Daniel Patrick Moynihan (D) of New York, who is co-sponsor of a tuition tax credit bill, hails the President. However, he sees ''some ground for concern'' that the administration has delayed its proposal so long, and he says: ''It may be impossible for this Congress to deal with this issue in the time remaining.''
Editorials discussed the matter before Mr. Reagan spoke and indicated its intensely controversial nature: The New York Times of April 14 called private school aid a ''bad idea.'' The Washington Post the same day called the plan ''bad law,'' ''bad economics,'' and ''bad public policy.'' On the other hand, some analysts said Mr. Reagan had been more conscientious in trying to carry out his campaign pledges than any other recent chief executive.
There are about 5 million students in private schools, of whom about 3.1 million were estimated to be in Roman Catholic schools in 1981, compared with 4. 4 million in 1971.
The proposal expected to come to Congress would provide a maximum tax credit of $500 over three years. By one estimate it would cost taxpayers $500 million the first year, rising to $1.5 billion. The aid would be deducted from income tax payments or returned as cash to those with low income taxes.
To aid the budget and reduce centralization, Mr. Reagan has proposed assorted cuts in federal aid to public education totaling about $2 billion, according to some estimates. The new proposal would cost approximately that amount, thereby shifting the aid from public schools and colleges to private schools.
Recent polls show erosion of middle-class support for the President, though his personal popularity remains high. The new program could affect his popularity.
Frank Monahan of the US Catholic Conference declared in a speech in Chicago, April 13, that the President's supporters want him to lobby vigorously for the proposed measure - or at least be perceived as ''going through the motions to give the appearance of making good on a campaign commitment.''