More than half the lawyers in the Justice Department's civil rights division have signed a letter protesting the role of their boss in the Reagan administration's decision to restore tax exemptions to private schools that discriminate.

The Jan. 26 letter to William Bradford Reynolds, assistant attorney general for civil rights, said reports that he provided the legal analysis supporting the change "cast serious doubt upon the division's commitment to enforce vigorously the nation's civil rights laws."

Sources said the letter was signed by more than 200 employes of the division, half of them lawyers. There are about 170 attorneys in the division and another 200 support personnel.

The letter said giving tax exemptions to racially discriminatory schools "violates existing federal civil rights law, as expressed in the Constitution, acts of Congress, and federal court interpretations thereof."

Reynolds told the Senate Finance Committee Monday that the 12-year-old policy reversal was justified because there is no reference to race in the original statute governing exemptions for educational organizations. A spokesman said yesterday that Reynolds' legal analysis will be distributed to the division's section offices and that Reynolds will then meet with employes who still have questions about his views.

This is the second protest by employes in the civil rights division since the Reagan administration took office and started rolling back traditional government stands on issues such as school desegregation and affirmative action.

Last September, more than 100 division attorneys sent a petition to Reynolds and Attorney General William French Smith expressing "profound concern" about what they considered a racist memo written by a Reynolds' deputy, Robert D'Agostino.

Reynolds' arguments in support of the effort to restore tax exemptions for discriminatory schools were challenged repeatedly during internal administration debate before the Jan. 8 announcement that reversed the 12-year-old policy of denying exemptions to discriminatory schools, according to memos turned over to the Finance Committee.

The administration backed off its Jan. 8 stance and now is supporting legislation to again block such exemptions. But there is no documentation that it was considering such legislation before the storm of protest that greeted the Jan. 8 announcement.

Peter Wallison, the Treasury Department general counsel who testified with Reynolds Monday, told Treasury Secretary Donald T. Regan in mid-December that the policy blocking exemptions for racist schools should be supported.

He also told Regan the White House should consider the issue. But he said the secretary shouldn't tell Rep. Trent Lott (R-Miss.) "since we may want to preserve the president's position of noninvolvement in this matter, whichever way it goes."

Lott had been pressing the administration to change its position supporting denial of exemptions for Bob Jones University and Goldsboro Christian Schools.

On Dec. 22, Wallison argued that a change in position "would be read as a statement by the administration that overtly discriminatory practices are not objectionable and as a significant retreat" from the past policies of Republican and Democratic administrations.

The administration's explanation, he added prophetically, "would be lost in the ensuing outcry."

The documents given to the committee show only Reynolds and Bruce E. Fein, an aide to Deputy Attorney General Edward C. Schmults, expressing support for the change, which has become a major public relations disaster for the president.

Fein told Schmults Dec. 7 that the existing government position "claims that the federal judiciary in these cases properly exercised a roving commission" to examine all potentially eligible exempt schools. He added that that position "seems to conflict with the attorney general's view that the department should discourage rather than encourage judicial activism and policy making."

Schmults testified Monday that the turnabout was prompted solely by the department's legal analysis, not politics. The documents, however, include a Dec. 8 note from Carolyn Kuhl, a special assistant to Smith, saying she had just run across "the attached relevant statements in the Republican platform and Reagan/Bush position papers."

Arguing against the change in position, besides Wallison, were IRS Commissioner Roscoe Egger, and attorneys in the Justice Department's tax division, solicitor general's office, and office of legal counsel, the documents show.

For instance, Assistant Attorney General Theodore B. Olson, in a memo to Smith and Schmults the day the reversal was announced, criticized the analysis in Reynolds' legal memo.

He cited several excerpts from Supreme Court opinions that said congressional silence on executive branch regulations could amount to acquiesence. Reynolds' memo was based on the opposing thesis that Congress had to address the issue specifically.

In an apparent reference to the rushed decision-making he was witnessing, Olson added: "This is a complicated issue and there has not been time, unfortunately, to review this in a manner which is consistent with the importance of the decision being made."