The Reagan administration is involved in a "major policy reversal" by limiting its investigation of discrimination at private schools and colleges and "unless promptly reversed could jeopardize fundamental civil rights protections," the U.S. Commission on Civil Rights stated yesterday.

In a separate statement, the commission--three of whose six members were fired by President Reagan last month pending Senate confirmation of their replacements--said it is "disappointed and concerned" about Reagan's record of appointing women and minoirities to his administration, the federal judiciary, the U.S. attorney's office and the Foreign Service.

The commission's statement on investigations of discrimination was prompted by a Supreme Court case, Grove City College v. Bell (the secretary of education) in which the Pennsylvania school challenged the government's right to require college officials to sign a pledge that their school does not violate Title IX of the Civil Rights Act, which bars discrimination against women.

According to the Civil Rights Commission, the Justice Department questions whether it can properly intervene in a case where a school only gets federal funds indirectly, through grants to students. The administration must decide its final posture in the case by July.

"Vital civil rights protections for women are at stake in Grove City College v. Bell," said commission member Jill S. Ruckelshaus. "A strong defense of broad Title IX coverage is needed to preserve and continue over 10 years of progress toward equal educational opportunity for women . . . the federal enforcement effort must not be narrowed."

In its statement on appointments, the commission said that women and minorities each hold only 8 percent of the top, full-time presidentially appointed jobs. By comparison, in October, 1980, the Carter administration had women in 17 percent of its highest jobs and minorities in 12 percent. Minority women are "virtually absent" from the Reagan administration, the report said.

"The availabilty of qualified women and minority men for full-time presidential appointments should not be in doubt," the report said. "For example, 1980 census figures show that more than one-third of all state legislators and more than 17 percent of all judges in our society are women. Recent elections in Chicago, Denver and Philadelphia indicate that black and Hispanic candidates for such offices as mayor are increasingly active and successful in public affairs."

Reagan, asked in Tennessee about the commission's report, defended his record in appointing women:

"Where women have been concerned there have never been three women in a Cabinet of the United States government before, and there are now," Reagan said. "And there is a woman who is a United States Supreme Court justice for the first time.

"And actually in the first two years of our administation we have appointed more women to high executive, policy-making positions than any administration we can find in that same period of time. And we're doing the utmost with regard to minority appointments, also."